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Punjab State Board PSEB 12th Class Chemistry Important Questions Chapter 8 The d-and f-Block Elements Important Questions and Answers.

PSEB 12th Class Chemistry Important Questions Chapter 8 The d-and f-Block Elements

Very Short Answer Type Questions

Question 1.
Why first ionisation enthalpy of Cr is lower than that of Zn?
Answer:
Ionisation enthalpy of Cr is less than that of Zn configuration. In case of zinc, electron comes out from completely filled 4s-orbital. So, removal of electron from zinc requires more energy as compared to the chromium.

Question 2.
Zn, Cd and Hg are soft metals. Why?
Answer:
Because they have one or more typical metallic structures at normal temperatures.

Question 3.
Although fluorine is more electronegative than oxygen, but the ability of oxygen to stabilise higher oxidation states exceeds that of fluorine. Why?
Answer:
Oxygen can form multiple bonds with metals, while fluorine can’t form multiple bond with metals. Hence, oxygen has more ability to stabilise higher oxidation state rather than fluorine.

Question 4.
Mn shows the highest oxidation state of + 7 with oxygen but with fluorine it shows the highest oxidation state of +4. Why?
Answer:
This is due to ability of oxygen to form pπ – dπ bond.

Question 5.
Mn₂O₇ is acidic whereas MnO is basic.
Answer:
Mn has +7 oxidation state in Mn₂O₇ and +2 in MnO. In low oxidation state of the metal, some of the valence electrons of the metal atom are not involved in bonding. Hence, it can donate electrons and behave as a base. On the other hand, in higher oxidation state of the metal, valence electrons are involved on bonding and are not available. Instead effective nuclear charge is high and hence it can accept electrons and behave as an acid.

Question 6.
Copper atom has completely filled d-orbitals in its ground state but it is a transition element. Why?
Answer:
Copper exhibits +2 oxidation state wherein it has incompletely filled d orbitals (3d⁹ 4s⁰) hence a transition elements.

Question 7.
Why is zinc not regarded as a transition element?
Answer:
As zinc atom has completely filled d-orbitals (3d10) in its ground state as well as oxidised state, therefore, it is not regarded as transition element.

Question 8.
Zn²⁺ salts are white while Cu²⁺ salts are coloured. Why?
Answer:
Cu²⁺(3d⁹4s⁰) has one unpaired electron in d-subshell which absorbs radiation in visible region resulting in d-d transition and hence Cu²⁺ salts are coloured. Zn²⁺(3d¹⁰4s⁰) has completely filled d-orbitals. No radiation is absorbed for d-d transition and hence Zn²⁺ salts are colourless.

Question 9.
The second and third row of transition elements resemble each other much more than they resemble the first row. Explain, why?
Answer:
Due to lanthanoid contraction, the atomic radii of the second and third row transition elements is almost same. So, they resemble each other much more as compared to first row elements and show similar character.

Question 10.
Why does copper not replace hydrogen from acids?
Answer:
Because Cu shows E^⊖ positive value.

Short Answer Type Questions

Question 1.
Why do transition elements show variable oxidation states? How is the variability in oxidation states of d-block different from that of the p-block elements?
Answer:
In transition elements, the energies of (n – 1)d orbitals and ns orbitals are nearly same. Therefore, electrons from both can participate in bond formation and hence show variable oxidation states.

In transition elements, the oxidation states differ from each other by unity e.g., Fe²⁺ and Fe³⁺, Cu⁺ and Cu²⁺ etc., while in p-block elements the oxidation state differ by units of two, e.g., Sn²⁺ and Sn⁴⁺, Pb²⁺ and Pb⁴⁺ etc. In transition elements, the higher oxidation states are more stable for heavier elements in a group e.g., Mo(VI) and W(VI) are more stable than Cr(VI) in group 6 whereas in p-block, elements the lower oxidation states are more stable for heavier elements due to the inert pair effect, e.g., Pb(II) is more stable than Pb(IV) in group 16.

Question 2.
When a chromite ore (A) is fused with sodium carbonate in free excess of air and the product is dissolved in water, a yellow solution of compound (B) is obtained. After treatment of this yellow solution with sulphuric acid, compound (C) can be crystallised from the solution. When compound (C) is treated with KC1, orange crystals of compound (D) crystallise out. Identify A to D and also explain the reactions.
Answer:
K₂Cr₂O₇ is an orange compound. It is formed when Na₂Cr₂O₇ reacts with KCl. In acidic medium, yellow coloured \(\mathrm{CrO}_{4}^{2-}\) (chromate ion) changes into dichromate.
The given process is the preparation method of potassium dichromate from chromite ore.
A = FeCr₂O₄; B = Na₂CrO₄; C = Na₂Cr₂O₇; D = K₂Cr₂O₇

Question 3.
Mention the type of compounds formed when small atoms like H, C and N get trapped inside the crystal lattice of transition metals. Also give physical and chemical characteristics of these compounds.
Answer:
When small atoms like H, C and N get trapped inside the crystal lattice of transition metals.
(a) Such compounds are called interstitial compounds.
(b) Their characteristic properties are :

1. They have high melting point, higher than those of pure metals.
2. They are very hard.
3. They retain metallic conductivity.
4. They are chemically inert.

Question 4.
On the basis of lanthanoid contraction, explain the following:
(i) Nature of bonding in La₂O₃ and Lu₂O₃.
(ii) Trends in the stability of oxosalts of lanthanoids from La to Lu.
(iii) Stability of the complexes of lanthanoids.
(iv) Radii of 4d and 5d block elements.
(v) Trends in acidic character of lanthanoid oxides.
Answer:
(i) As the size decreases covalent character increases. Therefore, La₂O₃ is more ionic and Lu₂O₃ is more covalent.
(ii) As the size decreases from La to Lu, stability of oxosalts also decreases.
(iii) Stability of the complexes increases as the size of lanthanoids decreases.
(iv) Radii of 4d and 5d block elements will be almost same.
(v) Acidic character of oxides increases from La to Lu.

Question 5.
A solution of KMnO₄ on reduction yields either a colourless solution of a brown precipitate or a green solution depending on pH of the solution. What different stages of the reduction do these represent and how are they carried out?
Answer:
Oxidising behaviour of KMnO₄ depends on pH of the solution.
In acidic medium (pH < 7),

Question 6.
Identify the following:
(i) Oxoanion of chromium which is stable in acidic medium.
(ii) The lanthanoid element that exhibits + 4 oxidation state.
Answer:
(i) Cr₂O₇
(ii) Cerium

Question 7.
The magnetic moments of few transition metal ions are given below:

Metal ion	Metal ion
Sc3+	0.00
Cr2+	4.90
Ni2+	2.84
Ti3+	1.73

(at no. Sc = 21, Ti = 22, Cr = 24, Ni = 28)
Which of the given metal ions :
(i) has the maximum number of unpaired electrons?
(ii) forms colourless aqueous solution?
(iii) exhibits the most stable + 3 oxidation state?
Answer:
(i) Cr²⁺
(ii) Sc³⁺
(iii) Sc³⁺

Question 8.
Consider the standard electrode potential values (M²⁺/M) of the elements of the first transition series.

Explain:
(i) E⁰ value for copper is positive.
(ii) E⁰ value of Mn is more negative as expected from the trend.
(iii) Cr²⁺ is a stronger reducing agent than Fe²⁺.
Answer:
(i) E⁰ value for copper is positive because the high energy to transform Cu(s) to Cu²⁺(aq) is not balanced by its hydration enthalpy.
(ii) E⁰ value of Mn is more negative as expected from the trend because Mn²⁺ has d⁵ configuration i. e., stable half-filled configuration.
(iii) Cr²⁺ is a stronger reducing agent than Fe²⁺ because d⁴ to d³ occurs in case of Cr²⁺ to Cr³⁺ (more stable \(t_{2 g}^{3}\)) while it changes from d⁶ to d⁵ in case of Fe²⁺ to Fe³⁺.

Long Answer Type Questions

Question 1.
Write similarities and differences between the chemistry of lanthanoids and that of actinoids.
Answer:
Similarities between lanthanoids and actinoids :

1. Both lanthanoids and actinoids mainly show an oxidation state of +3.
2. Actinoids show actinoid contraction like lanthanoid contraction is exhibited by lanthanoids.
3. Both lanthanoids and actinoids are electropositive.

Differences between lanthanoids and actinoids :

1. The members of lanthanoid exhibit less number of oxidation states than the corresponding members of actinoid series.
2. Lanthanoid contraction is smaller than the actinoid contraction.
3. Lanthanoids except promethium cure non-radioactive metals while actinoids are radioactive metals.

Question 2.
(a) Assign reasons for the following:
(i) Zr and Hf have almost identical radii.
(ii) The , value for copper is positive (+0.34 V).
(b) Although +3 oxidation state is the characteristic oxidation state of lanthanoids but cerium shows +4 oxidation state also. Why?
Answer:
(a) (i) This is due to filling of 4/ orbitals which have poor shielding effect (lanthanoid contraction).
(ii) This is because the sum of enthalpies of sublimation and ionisation is not balanced by hydration enthalpy.
(b) It is because after losing one more electron Ce acquires stable 4f⁰ electronic configuration.

Question 3.
(a) How do you prepare :
(i) K₂MnO₄ from MnO₂?
(ii) Na₂Cr₂O₇ from Na₂CrO₄?
(b) Account for the following :
(i) The enthalpy of atomisation is lowest for Zn in 3d series of the transition elements.
(ii) Actinoid elements show wide range of oxidation states.
Answer:
(a) (i) Pyrolusite is fused with KOH in the presence of atmospheric oxygen to give K₂MnO₄.

(b) (i) In the formation of metallic bonds, no electrons from 3d-orbitals are involved in case of zinc, while in all other metals of the 3d series, electrons from the d-orbitals are always involved in the formation of metallic bonds. That is why the enthalpy of atomisation of zinc is the lowest in the series.
(ii) This is due to comparable energies of 5f, 6d and 7s orbitals.

Punjab State Board PSEB 12th Class Physics Book Solutions Chapter 6 Electromagnetic Induction Textbook Exercise Questions and Answers.

PSEB Solutions for Class 12 Physics Chapter 6 Electromagnetic Induction

PSEB 12th Class Physics Guide Electromagnetic Induction Textbook Questions and Answers

Question 1.
Predict the direction of induced current in the situations described by the following Figs. 6.18 (a) to (f).


Answer:
(a) As the magnet moves towards the solenoid, the magnetic flux linked with the solenoid increases. According to Lenz’s law, the induced e.m.f. produced in the solenoid in such that it opposes the very cause producing it i. e., it opposes the motion of the magnet. Hence the face q of it becomes the south pole and p becomes north pole. Therefore, the current will flow along pqin the coili. e., along qrpqin this figurei. e., clockwise when seen from the side of the magnet according to clock rule.

(b) As the north pole moves away from xy coil, so the magnetic flux linked with this coil decreases. Thus according to Lenz’s law, the induced e.m.f. produced in the coil will oppose the motion of the magnet. Hence the face, X becomes S-pole, so the current will flow in the clockwise direction i.e., along yzx in the cone.

For coil pq, the south pole of the magnet moves towards end q and thus this end will acquire south polarity so as to oppose the motion of the magnet, hence the current will flow along prq in the coil.

(c) The induced current will be in the anticlockwise direction i.e., along yzx.

(d) The induced current will be in the clockwise direction i.e., along zyx.

(e) The battery current in the left coil will be from right to left, so by mutual induction, the induced current in the right coil will be in the opposite direction i.e., from left to right or along xry.

(f) In this case, there is no change in magnetic flux linked with the wire, so no current will flow through the wire since there is no induced current as the field lines lie in the plane of the loop.

Question 2.
Use Lenz’s law to determine the direction of induced current in the situations described by Fig. 6.19.
(a) A wire of irregular shape turning into a circular shape;
(b) A circular loop being deformed into a narrow straight wire.

(a) When a wire of irregular shape turns into a circular loop, the magnetic flux linked with the loop increases due to increase in area. The circular loop has greater area than the loop of irregular shape. The induced e.m.f. will cause current to flow in such a direction so that the wire forming the loop is pulled inward from all sides i.e., current must flow in the direction adcba as shown in Fig. (a) i.e., in anticlock-wise direction so that the magnetic field produced by the current ((directed out of the paper) opposes the applied field.

In Fig. (b), a circular loop deforms into a narrow straight wire i.e., upper side of loop should move downwards and lower end should move upwards to oppose the motion of the circular loop, thus its area decreases as a result of which the magnetic flux linked with it decreases. To oppose the decrease in magnetic flux, the induced current should flow anti clockwise in the loop i. e., along a’d’ d b’ a’. Due to the flow of anti-clockwise current, the magnetic field produced will be out of the page and hence the applied field is supplemented.

Question 3.
A long solenoid with 15 turns per cm has a small loop of area 2.0 cm² placed inside the solenoid normal to its axis. If the current carried hy the solenoid changes steadily from 2.0 A to
4.0 A in 0.1 s, what is the induced emf in the loop while the current is changing?
Answer:
Number of turns per unit length of the solenoid, n = 15 turns/cm = 1500 turns/m
The solenoid has a small loop of area, A = 2.0 cm² = 2 × 10^-4 m²
Current carried by the solenoid changes from 2 A to 4 A.
.-. Change in current in the solenoid, dI = 4 – 2 = 2A
Change in time, dt = 0.1 s
We know that the magnetic field produced inside the solenoid is given by
B = μ₀nI
If Φ be the magnetic flux linked with the loop, then
Φ = BA = μ₀nI A
Induced emf in the solenoid is given by Faraday’s law as
e = –\(\frac{d \phi}{d t}\)
e = – \(\frac{d}{d t}\) (Φ) = –\(\frac{d}{d t}\) μ₀nI A
μ₀n A \(\frac{d I}{d t}\)
∴ Magnitude of e is given by
= A μ₀n × (\(\frac{d I}{d t}\))
= 2 × 10^-4 × 4π × 10^-7 × 500 × \(\frac{2}{0.1}\)
7.54 × 10 ^-6 V
Hence, the induced voltage in the loop is = 7.54 × 10 ^-6 V

Question 4.
A rectangular wire loop of sides 8 cm and 2 cm with a small cut is moving out of a region of uniform magnetic field of magnitude 0.3 T directed normal to the loop. What is the emf developed across the cut if the velocity of the loop is 1 cm s^-1 in a direction normal to the (a) longer side, (b) shorter side of the loop? For how long does the induced voltage last in each case?
Answer:
Length of the rectangular wire, l = 8 cm = 0.08 m
Width of the rectangular wire, b = 2 cm = 0.02 m
Hence, area of the rectangular loop A = lb
= 0.08 × 0.02
= 16 × 10^-4 m²
Magnetic field strength, B = 0.3 T
Velocity of the loop, v = 1 cm/s = 0.01 m / s

(a) Emf developed in the loop is given as
e = Blv
= 0.3 × 0.08 × 0.01 = 2.4 × 10^-4 V

= \(\frac{b}{v}\) = \(\frac{0.02}{0.01}\) = 2 s
Hence, the induced voltage is 2.4 × 10^-4 V which lasts for 2s.

(b) Emf developed,
e = Bbv = 0.3 × 0.02 × 0.01 = 0.6 × 10^-4 V

\(\frac{l}{v}\) = \(\frac{0.08}{0.01}\) 8s
Hence, the induced voltage is 0.6 × 10^-4 V which lasts for 8 s.

Question 5.
A 1.0 m long metallic rod is rotated with an angular frequency of 400 rad s^-1 about an axis normal to the rod passing through its one end. The other end of the rod is in contact with a circular metallic ring. A constant and uniform magnetic field of 0.5 T parallel to the axis exists everywhere. Calculate the emf developed between the centre and the ring.
Answer:
Length of the rod, l = 1m
Angular frequency, ω = 400 rad/s
Magnetic field strength, B = 0.5 T
One end of the rod has zero linear velocity, while the other end has a linear velocity of l ω.
Average linear velocity of the rod, v = \(\frac{l \omega+0}{2}=\frac{l \omega}{2}\)
Emf developed between the centre and the ring,
e = Blv = Bl(\(\frac{l \omega}{2}\)) = \(\frac{B l^{2} \omega}{2}\)
= \(\frac{0.5 \times(1)^{2} \times 400}{2}\) = 100V
Hence, the emf developed between the centre and the ring is 100 V.

Question 6.
A circular coil of radius 8.0 cm and 20 turns is rotated about its vertical diameter with an angular speed of 50 rad s^-1 in a uniform horizontal magnetic field of magnitude 3.0 × 10^-2 T. Obtain the maximum and average emf induced in the coil. If the coil forms a closed loop of resistance 10 Ω, calculate the maximum value of current in the coil. Calculate the average power loss due to Joule heating. Where does this power come from?
Answer:
Here, n = number of turns in the coil = 20
r = radius ofcoil = 8.0 cm = 8 × 10^-2 m
ω = angular speed of the coil = 50 rad s^-1.
B = magnetic field = 3.0 × 10^-2 T
Let e₀ be the maximum e.m.f. in the coil = ?
and e_av be the average e.m.f. in the coil = ?
We know that the instantaneous e.m.f. produced in a coil is given by
e = BA ω sinωt.
for e to be maximum e_max, sin ωt = 1.
∴ e_max = B A n ω = B.πr² nω
where A = πr² is the area of the coil

i.e., e_av is zero as the average value of sincot for one complete cycle is always zero.
Now R = resistance of the closed loop formed by the coil = 10 Ω
Let I_max = maximum current in the coil = ?
∴ Using the relation,
I_max = \(\frac{e_{\max }}{R}\), we get
I_max = \(\frac{0.603}{10}\) = 0.0603 A
Let P_av be the average power loss due to Joule heating = ?
∴ P_av = \(\frac{e_{\max } \cdot I_{\max }}{2}\) = \(\frac{0.603 \times 0.0603}{2}\)
= 0.018 Watt
The induced current causes a torque opposing the rotation of the coil. An external agent must supply torque and do work to counter this torque in order to keep the coil rotating uniformly. Thus the source of the power dissipated as heat in the coil is the external agent i. e., rotor.

Question 7.
A horizontal straight wire 10 m long extending from east to west is falling with a speed of 5.0 m s^-1, at right angles to the horizontal component of the earth’s magnetic field, 0.30 × 10^-4 Wb m^-2.
(a) What is the instantaneous value of the emf induced in the wire?
(b) What is the direction of the emf?
(c) Which end of the wire is at the higher electrical potential?
Answer:
Length of the wire, l = 10 m
Falling speed of the wire, v = 5.0 m/s
Magnetic field strength, B = 0.3 × 10^-4 Wb m^-2

(a) emf induced in the wire,
e = Blv = 0.3 × 10^-4 × 5 × 10
= 1.5 × 10^-3 V

(b) Using Fleming’s right hand rule, it can be inferred that the direction of the induced emf is from west to east.

(c) The eastern end of the wire is at a higher electrical potential.

Question 8.
Current in a circuit falls from 5.0 A to 0.0 A in 0.1 s. If an average emf of 200 V induced, give an estimate of the self-inductance of the circuit.
Initial current, I₁ = 5.0 A
Final current, I₂ = 0.0 A
Change in current, dl = I₁ – I₂ = 5 – 0 = 5 A
Time taken for the change, dt = 0.1 s
Average emf, e = 200 V
For self-inductance (I) of the circuit, we have the relation for average emf as
e = L\(\frac{d I}{d t}\)
L = \(\frac{e}{\left(\frac{d I}{d t}\right)}\)
= \(\frac{200}{\frac{5}{0.1}}=\frac{200 \times 0.1}{5}\) 4H
Hence, the self induction of the circuit is 4 H.

Question 9.
A pair of adjacent coils has a mutual inductance of 1.5 H. If the current in one coil changes from 0 to 20 A in 0.5 s, what is the change of flux linkage with the other coil?
Answer:
Mutual inductance of the pair of coils, μ = 1.5 H
Initial current, I₁ = 0 A
Final current, I₂ – 20 A
Change in current, dI = I₂ – I₁ = 20 – 0 = 20 A
Time taken for the change, dt = 0.5 s
Induced emf, e = \(\frac{d \phi}{d t}\) ………… (1)

Where d Φ is the change in the flux linkage with the coil.
Emf is related with mutual inductance as
e = μ\(\frac{d I}{d t}\) ……………. (2)
Equating equations (1) and (2), we get
\(\frac{d \phi}{d t}\) = μ\(\frac{d I}{d t}\)
or dΦ = μdI
∴ dΦ = 1.5 × (20) = 30 Wb
Hence, the change in the flux linkage is 30 Wb.

Question 10.
A jet plane is travelling towards west at a speed of 1800 km/h. What is the voltage difference developed between the ends of the wings having a span of 25 m, if the Earth’s magnetic field at the location has a magnitude of 5 × 10^-4 T and the dip angle is 30°.
Answer:
Speed of the jet plane, v = 1800 km/h = 1800 × \(\frac{5}{18}\) = 500 m/s
Wing span of the jet plane, l = 25 m
Earth’s magnetic field strength, B = 5.0 × 10^-4 T
Angle of dip, δ = 30°
Vertical component of Earth’s magnetic field,
B_V = B sinδ
= 5 × 10^-4 × sin30°
= 5 × 10^-4 × \(\frac{1}{2}\) = 2.5 × 10^-4 T
Voltage difference between the ends of the wing can be calculated as
e = (B_V) × l × v
= 2.5 × 10^-4 × 25 × 500 = 3.125 V
Hence, the voltage difference developed between the ends of the wings is 3.125 V.

Question 11.
Suppose the loop in Exercise 6.4 is stationary but the current feeding the electromagnet that produces the magnetic field is gradually reduced so that.the field decreases from its initial value of 0.3 T at the rate of 0.02 Ts^-1. If the cut is joined and the loop has a resistance of 1.6 Ω, how much power is dissipated by the loop as heat? What is the source of this power?
Answer:
Sides of the rectangular wire loop are 8 cm and 2 cm.
Hence, area of the rectangular wire loop,
A = length × width = 8 × 2 = 16 cm
= 16 × 10^-4 m²
Initial value of the magnetic field, B = 0.3 T
Rate of decrease of the magnetic field, \(\frac{d B}{d t}\) = 0.02 T/s
emf developed in the loop is given as
e = \(\frac{d \phi}{d t}\)
where, Φ = Change in flux through the loop area
= AB
∴ e = \(\frac{d(A B)}{d t}=\frac{A d B}{d t}\)
= 16 × 10^-4 × 0.02 =0.32 × 10^-4 V
= 3.2 × 10^-5 V
Resistance of the loop, R = 1.6 Ω
The current induced in the loop is given as
i = \(\frac{e}{R}\)
= \(\frac{0.32 \times 10^{-4}}{1.6}\) = 2 × 10^-5A
Power dissipated in the loop in the form of heat is given as
P = i²R
= (2 × 10^-5)² × 1.6
= 6.4 × 10^-10 W
The source of this heat loss is an external agent, which is responsible for changing the magnetic field with time.

Question 12.
A square loop of side 12 cm with its sides parallel to X and F axes is moved with a velocity of 8 cm s^-1 in the positive x-direction in an environment containing a magnetic field in the positive 2-direction. The field is neither uniform in space nor constant in time. It has a gradient of 10^-3 T cm^-1 along the negative jtr-direction (that is it increases by 10^-3 T cm^-1 as one moves in the negative x-direction), and it is decreasing in time at the rate of 10-3 T s1. Determine the direction and magnitude of the induced current in the loop if its resistance is 4.50 mΩ.
Answer:
Here, a = side of the square loop = 12 cm = 12 × 10^-2 m
\(\vec{v}\) = velocity of loop parallel to x-axis = 8 cms^-1
= 8 × 10^-2 ms^-1.
Let B = variable magnetic field acting away from us ⊥ ar to the XY plane along z axis i. e., plane of paper represented by x.
\(\) = 10^-3 Tcm^-1
= 10^-3 × 10² Tm^-1
= 0.1 Tm^-1
= field gradient along – ve x direction.

\(\frac{d B}{d t}\) = rate of variation with me
= 10^-3 Ts^-1
R = resistance of the loop = 4.5 mΩ = 4.5 × 10^-3 Ω
Let I = induced current = ? and its direction = ?
∴ A = area of loop = a² = (12 × 10^-2)² m² = 144 × 10^-4 m².
The magnetic flux changes (i) due, to the variation of B with time and
(ii) due to motion of the loop in non-uniform \(\vec{B}\).
Thus if Φ be the total magnetic flux of the loop, then Φ is calculated as Area of shaded part = adx
Let dΦ = magnetic flux linked with shaded part = B(x,t)adx

∴ From (3), \(\) = 144 × 10^-7 + 1152 × 10^-7
= 1296 × 10^-7 Wbs^-1
Clearly the two effect add up as these cause a decrease in flux along the + z direction.
∴ If e be the induced e.m.f. produced, then
e = –\(\frac{d \phi}{d t}\) = -1296 × 10^-7 V
= -12.96 × 10^-5 V
∴ e = 12.96 × 10^-5 V
∴ I = \(\frac{e}{R}\) = \(\frac{12.96 \times 10^{-5}}{4.5 \times 10^{-3}}\) 2.88 × 10^-2 A.
The direction of induced current is such as to increase the flux through the loop along +z-direction. Thus if for the observer, the loop moves to the right, the current will be seen to be anti-clockwise.

Question 13.
It is desired to measure the magnitude of field between the poles of a powerful loud speaker magnet. A small fiat search coil of area 2 cm² with 25 closely wound turns, is positioned normal to the field direction, and then quickly snatched out of the field region. Equivalently, one can give it a quick 90° turn to bring its plane parallel to the field direction. The total charge flown in the coil (measured by a ballistic galvanometer connected to coil) is 7.5 mC. The combined resistance of the coil and the galvanometer is 0.50 Q. Estimate the field strength of magnet.
Answer:
Area of the small flat search coil, A = 2cm² = 2 × 10^-4m²
Number of turns on the coil, N = 25
Total charge flown in the coil, Q = 7.5 mC = 7.5 × 10 ^-3 C
Total resistance of the coil and galvanometer, R = 0.50 Ω
Induced current in the coil,
I = \(\frac{\text { Induced emf }(e)}{R}\) ………….. (1)
Induced emf is given us
e = -N\(\frac{d \phi}{d t}\) ……………… (2)
Combining equations (1) and (2), we get


Hence, the field strength of the magnet is 0.75 T.

Question 14.
Figure 6.20 shows a metal rod PQ resting on the smooth rails AB and positioned between the poles of a permanent magnet. The rails, the rod, and the magnetic Held are in three mutual perpendicular directions. A galvanometer G connects the rails through a switch K. Length of the rod = 15 cm, B = 0.50 T, resistance of the closed loop containing the rod = 9.0 mfl. Assume the field to be uniform.

(a) Suppose K is open and the rod is moved with a speed of 12 cm s^-1 in me airection snown. dive me polarity ana magnitude of the induced emf.

(b) Is there an excess charge built up at the ends of the rods when K is open? What if K is closed?

(c) With K open and the rod moving uniformly, there is no net force on the electrons in the rod PQ even though they do experience magnetic force due to the motion of the rod. Explain.

(d) What is the retarding force on the rod when K is closed?

(e) How much power is required (by an external agent) to keep the rod moving at the same speed (= 12 cm s^-1) when K is closed? How much power is required when K is open?

(f) How much power is dissipated as heat in the closed circuit? What is the source of this power?

(g) What is the induced emf in the moving rod if the magnetic field is parallel to the rails instead of being perpendicular?
Answer:
Here, B = 0.50 T
l = length of the rod = 15 cm = 15 × 10^-2 m
R = resistance of the closed loop containing the rod = 9.0 mΩ
= 9 × 10^-3 Ω.

(a) v = speed of the rod = 12 cms^-1 = 12 × 10^-2 ms^-1.
The magnitude of the induced e.m.f. is
E = Blv = 0.50 × 15 × 10^-2 × 12 × 10^-12 = 9 × 10^-3 V
According to Fleming’s left hand rule, the direction of Lorentz force —^ ^ ^
\(\vec{F}\) = -e(\(\vec{V} \times \vec{B}\)) on electrons in PQ is from P to Q. So the end P of the rod will acquire positive charge and Q will acquire negative charge,

(b) Yes. When the switch K is open, the electrons collect at the end Q, so excess charge is built up at the end Q. But when the switch K is closed, the accumulated charge at the end Q is maintained by the continuous flow of current.

(c) This is because the presence of excess charge at the ends P and Q of the rod sets up an electric field \(\vec{E}\). The force due to the electric field (q\(\vec{E}\)) balances the Lorentz magnetic force q(\(\vec{V} \times \vec{B}\)). Hence the net force on the electrons is zero.

(d) When the key K is closed, current flows through the rod. The retarding force experienced by the rod is
F = BIl = B(\(\frac{E}{R}\)) l
where, I = \(\) is the induced current. R
F = \(\frac{0.50 \times 9 \times 10^{-3} \times 15 \times 10^{-2}}{9 \times 10^{-3}}\)
= 7.5 × 10^-2 N.

(e) The power required by the external agent against the above retarding force to keep the rod moving uniformly at speed 12 cms^-1 (= 12 × 10^-2 m/s) when K is closed is given by
p = FV = 7. 5 × 10^-2 × 12 × 10^-2
= 90 × 10^-4 W
= 9 × 10^-3 W

(f) Power dissipated as heat is given by
P = I²R = (\(\frac{E}{R}\))² R = \(\frac{E^{2}}{R}\)
= \(\frac{\left(9 \times 10^{-3}\right)^{2}}{9 \times 10^{-3}}\)
= 9 × 10^-3 W.
The source of this power is the power provided by the external agent calculated in (e).

Zero. This is because when the magnetic field is parallel to the rails, θ = 0°, so induced e.m.f. E = Blv sinθ = Blv sin 0 = 0. In this situation, the moving rod does not cut the field lines, so there is no change in the magnetic flux, hence E = 0.

Question 15.
An air-cored solenoid with length 30 cm, area of cross-section 25 cm² and number of turns 500, carries a current of 2.5 A. The current is suddenly switched off in a brief time of 10^-3 s. How much is the average back emf induced across the ends of the open switch in the circuit? Ignore the variation in magnetic Held near the ends of the solenoid.
Answer:
Length of the solenoid, l = 30 cm = 0.3 m
Area of cross-section, A = 25 cm² = 25 x 10^-4 m²
Number of turns on the solenoid, N = 500
Current in the solenoid, I = 2.5 A
Current flows for time, t = 10^-3 s
Average back emf, e = \(\frac{d \phi}{d t}\) ……………. (1)
where,
dΦ = NAB ………….. (2)
and B = μ₀ \(\frac{N I}{l}\) …………. (3)
Using equations (2) and (3) in equation (1), we get
e = \(\frac{\mu_{0} N^{2} I A}{l t}\)
\(=\frac{4 \pi \times 10^{-7} \times(500)^{2} \times 2.5 \times 25 \times 10^{-4}}{0.3 \times 10^{-3}}\)
= 6.5 V
Hence, the average back emf induced in the solenoid is 6.5 V.

Question 16.
(a) Obtain an expression for the mutual inductance between a long straight wire and a square loop of side a as shown in Figure 6.21.

(b) Now assume that the straight wire carries a current of 50 A and the loop is moved to the right with a constant velocity, v = 10 m/s.
Calculate the induced emf in the loop at the instant when x = 0.2 m.
Take a = 0.1 m and assume that the loop has a large resistance.
Answer:
(a) Take a small element dy in the loop at a distance y from the long straight wire (as shown in the given figure).
Magnetic flux associated with element dy, dΦ = BdA

= where,
dA = Area of element dy = a dy
B = Magnetic field at distance y = \(\frac{\mu_{0} I}{2 \pi y}\)
I = Current in the wire

Question 17.
A line charge λ per unit length is lodged uniformly onto the rim of a wheel of mass M and radius R. The wheel has light non-conducting spokes and is free to rotate without friction about its axis as shown in Fig. 6.22. A uniform magnetic field extends over a circular region within the rim. It is given by,
B = -Bk (r ≤ a; a < R)
= 0 (otherwise)
What is the angular velocity of the wheel after the field is suddenly switched off?

Answer:
Let ω be the angular velocity of the wheel of mass M and radius R.
Let e = Induced e.m.f. produced.
The rotational K.E. of the rotating wheel = \(\frac{1}{2}\) Iω² ………… (1)
where, I = Moment of inertia of wheel
= \(\frac{1}{2}\) MR² …………… (2)

or Work done = eQ
Applying the work energy theorem, we get
Rotational K.E. = Work done
or RotationalK.E. = Q × e …………… (3)
We know that the e.m.f. of a rod rotating in a uniform magnetic field is
given by \(\frac{1}{2}\) Bωa² , since here the magnetic field is changing, we assume the average over the time span and thus average value of e.m.f. is given by

Punjab State Board PSEB 12th Class Chemistry Important Questions Chapter 4 Chemical Kinetics Important Questions and Answers.

PSEB 12th Class Chemistry Important Questions Chapter 4 Chemical Kinetics

Very Short Answer Type Questions

Question 1.
For which type of reactions, order and molecularity have the same value?
Answer:
If the reaction is an elementary reaction, order is same as molecularity.

Question 2.
Why is the probability of reaction with molecularity higher than three very rare?
Answer:
The probability of more than three molecules colliding simultaneously is very small. Hence, possibility of molecularity being three is very low.

Question 3.
State a condition under which a bimolecular reaction is kinetically first order.
Answer:
A bimolecular reaction may become kinetically of first order if one of the reactants is in excess.

Question 4.
Thermodynamic feasibility of the reaction alone cannot decide the rate of the reaction. Explain with the help of one example.
Answer:
Thermodynamically the conversion of diamond to graphite is highly feasible but this reaction is very slow because its activation energy is high.

Question 5.
Why is it that instantaneous rate of reaction does not change when a part of the reacting solution is taken out?
Answer:
Instantaneous rate is measured over a very small interval of time, hence, it does not change when a part of solution is taken out.

Question 6.
A reaction is 50% complete in 2 hours and 75% complete in 4 hours. What is the order of the reaction?
Solution:
As t_75% = 2t_50%
Therefore, it is a first order reaction.

Question 7.
Define threshold energy of a reaction.
Answer:
Threshold energy is the minimum energy which must be possessed by reacting molecules in order to undergo effective collision which leads to formation of product molecules.

Question 8.
Why does the rate of a reaction increase with rise in temperature?
Answer:
At higher temperatures, larger fraction of colliding particles can cross the energy barrier (i.e., the activation energy), which leads to faster rate.

Question 9.
What is the difference between rate law and law of mass action?
Answer:
Rate law is an experimental law. On the other hand, law of mass action is a theoretical law based on the balanced chemical reaction.

Question 10.
What do you understand by ‘Rate of reaction’?
Answer:
The change in the concentration of any one of the reactants or products per unit time is termed as the rate of reaction.

Question 11.
In the Arrhenius equation, what does the factor e a corresponds to?
Answer:
e^-E_a/RT corresponds to the fraction of molecules that have kinetic energy greater than E_a,

Short Answer Type Questions

Question 1
What do you understand by the ‘order of a reaction’? Identify the reaction order from each of the following units of reaction rate constant:
(i) L^-1mols^-1
(ii) Lmol^-1s^-1.
Solution:
The sum of powers of the concentration of the reactants in the rate law expression is called order of reaction.
For a general reaction: aA + bB → Products
If rate = k[A]^m [B]ⁿ; order of reaction = m + n

(i) General unit of rate constant, k = (mol L^-1 )^1-ns^-1
L^-1mol s^-1 = (mol L^-1 )^1-ns^-1
-1 = -1 + n ⇒ n = 0 ∴ Reaction order = 0

(ii) L mol^-1 s^-1 = (mol L^-1)^1-n s^-1
1 = -1 + n ⇒ n = 2 ∴ Reaction order = 2

Question 2.
The rate constant for the first order decomposition of H₂O₂ is given by the following equation :
log k = 14.2 – \(\frac{1.0 \times 10^{4}}{T}\)K
Calculate E_a for this reaction and rate constant k if its half-life period be 200 minutes.
(Given: R = 8.314 JK^-1 mol^-1)
Solution:
Comparing the equation, log k = 14.2 – \(\frac{1.0 \times 10^{4}}{T}\) K with the equation,
log k = log A = \(\frac{E_{a}}{2.303 R T}\), we get
\(\frac{E_{a}}{2.303 R}\) = 1.0 × 10⁴ K or E_a = 1.0 × 10⁴ K × 2.303 × R
E_a = 1.0 × 10⁴ K × 2.303 × 8.314 JK^-1
= 19.1471 × 10⁴ Jmol^-1
= 191.47 kJ mol^-1
For a first order reaction, t_t/2 = \(\frac{0.693}{k}\) or k = \(\frac{0.693}{t_{1 / 2}}\)
k = \(\frac{0.693}{200 \mathrm{~min}}\) = 3.465 × 10 ^-3min^-1

Question 3.
The reaction, N₂(g) + O₂(g) ⇌ 2NO(g) contributes to air pollution whenever a fuel is burnt in air at a high temperature. At 1500 K, equilibrium constant K for it is 1.0 × 10^-5. Suppose in a case [N₂] = 0.80 mol L^-1 and [O₂] = 0.20 mol L^-1 before any reaction occurs. Calculate the equilibrium concentrations of the reactants and the product after the mixture has been heated to 1500 K.
Solution:

[N₂] = 0.8 – 6.324 × 10⁴ mol L^-1
= 0.799 molL^-1
[O₂] = 0.2 – 6.324 × 10^-4 mol L^-1
= 0.199 mol L^-1

Question 4.
For a general reaction, A → B, plot of concentration of A vs time is given in figure. Answer the following questions on the basis of this graph.

(i) What is the order of the reaction?
(ii) What is the slope of the curve?
(iii) What are the units of rate constant?
Answer:
(i) Zero order
(ii) Slope = – k
(iii) Units of rate constant = mol L^-1 s^-1

Question 5.
For a reaction, A + B → products, the rate law is rate = k [A][B]a^3/2. Can the reaction be an elementary reaction? Explain.
Answer:
During an elementary reaction, the number of atoms or ions colliding to react is referred to as molecularity. Had this been an elementary reaction the order of reaction with respect to B would have been 1, but in the given rate law it is \(\frac{3}{2}\). This indicated that the reaction is not an elementary reaction.

Question 6.
The rate constant for a first order reaction is 60 s^-1. How much time will it take to reduce 1 g of the reactant to 0.0625 g?
Answer:
We know that, t = \(\frac{2.303}{k}\) log \(\frac{[R]_{0}}{[R]}\)
t = \(\frac{2.303}{60}\) log \(\frac{1}{0.0625}\)
t = 0.0462 s

Long Answer Type Questions

Question 1.
For the hydrolysis of methyl acetate in aqueous solution, the following results were obtained:

t/s	0	30	60
[CH3COOCH3]/mol L-1	0.60	0.30	0.15

(i) Show that it follows pseudo first order reaction, as the concentration of water remains constant.
(ii) Calculate the average rate of reaction between the time interval 30 to 60 seconds.
(Given log 2 = 0.3010, log 4 = 0.6021)
Solution:

As the value of k is same in both the cases, therefore, hydrolysis of methylacetate in aqueous solution follows pseudo first order reaction.

(ii) Average rate = \(-\frac{\Delta\left[\mathrm{CH}_{3} \mathrm{COOCH}_{3}\right]}{\Delta t}\)
= \(\frac{-[0.15-0.30]}{60-30}\) = \(\frac{0.15}{30}\)
Average rate = 0.005 mol L^-1s^-1

Question 2.
Describe how does the enthalpy of reaction remain unchanged when a catalyst is used in the reaction?
Answer:
A catalyst is a substance which increases the speed of a reaction without itself undergoing any chemical change.
According to “intermediate complex formation theory” reactants first combine with the catalyst to form an intermediate complex which is short-lived and decomposes to form the products and regenerating the catalyst.

The intermediate formed has much lower potential energy than the intermediate complex formed between the reactants in the absence of the catalyst.

Thus, the presence of catalyst lowers the potential energy barrier and the reaction follows a new alternate pathway which require less activation energy.

We know that, lower the activation energy, faster is the reaction because more reactant molecules can cross the energy barrier and change into products.

Enthalpy, △H is a ‘state function. Enthalpy of reaction, i.e., difference in energy between reactants and product is constant, which is clear from potential energy diagram.
Potential energy diagram of catalysed reaction is given as:

Question 3.
All energetically effective collisions do not result in a chemical change. Explain with the help of an example.
Answer:
Only effective collision lead to the formation of products. It means that collisions in which molecules collide with sufficient kinetic energy (called threshold energy = activation energy + energy possessed by reacting species).

And proper orientation lead to a chemical change because it facilitates the breaking of old bonds between (reactant) molecules and formation of the new ones i.e., in products.
e.g., formation of methanol from bromomethane depends upon the orientation of the reactant molecules.

The proper orientation of reactant molecules leads to bond formation whereas improper orientation makes them simply back and no products are formed.

To account for effective collisions, another factor P (probability of steric factor) is introduced K = PZ_ABe^-Ea/RT.

Punjab State Board PSEB 12th Class Physics Book Solutions Chapter 7 Alternating Current Textbook Exercise Questions and Answers.

PSEB Solutions for Class 12 Physics Chapter 7 Alternating Current

PSEB 12th Class Physics Guide Alternating Current Textbook Questions and Answers

Question 1.
A 100 Ω resistor is connected to a 220 V, 50 Hz ac supply.
(a) What is the rms value of current in the circuit?
(b) What is the net power consumed over a full cycle?
Answer:
The given voltage of 220 V is the rms or effective voltage.
Given V_rms = 220 V, v = 50 Hz, R = 100 Ω
(a) RMS value of current,
I_rms = \(\frac{V_{r m s}}{R}\) = \(\frac{220}{100}\) = 2.2 A
Net power consumed, P = I²_rmsR
= (2.20)² × 100 = 484 W

Question 2.
(a) The peak voltage of an ac supply is 300 V. What is the rms voltage?
(b) The rms value of current in an ac circuit is 10 A. What is the peak current?
Answer:
(a) Given, V₀ = 300 V
V_rms = \(\frac{V_{0}}{\sqrt{2}}=\frac{300}{\sqrt{2}}\) = 150√2 ≈ 212 V

(b) Given, I_rms = 10 A
I₀ = I_rms √2 = 10 × 1.41 = 14.1 A

Question 3.
A 44 mH inductor is connected to 220 V, 50 Hz ac supply. Determine the rms value of the current in the circuit.
Answer:
Inductance of inductor, L = 44 mH = 44 × 10^-3 H
Supply voltage, V = 220 V
Frequency, v = 50 Hz
Angular frequency, ω = 2 πv
Inductive reactance, X_L = ωL = 2πvL × 2π × 50 × 44 × 10^-3Ω
rms value of current is given as
I = \(\frac{V}{X_{L}}\) = \(\frac{220}{2 \pi \times 50 \times 44 \times 10^{-3}}\) = 15.92 A
Hence, the rms value of current in the circuit is 15.92 A.

Question 4.
A 60 μF capacitor is connected to a 110 V, 60 Hz ac supply. Determine the rms value of the current in the circuit.
Answer:
Capacitance of capacitor, C = 60μF = 60 × 10^-6F
Supply voltage, V = 110 V
Frequency, v = 60 Hz
Angular frequency, ω = 2 πv
Capacitive reactance,
X_C = \(\frac{1}{\omega C}\) = \(\frac{1}{2 \pi v C}\) = \(\frac{1}{2 \pi \times 60 \times 60 \times 10^{-6}}\)Ω
rms value of current is given as
I = \(\frac{V}{X_{C}}\) = \(\frac{110}{\frac{1}{2 \pi \times 60 \times 60 \times 10^{-6}}}\)
= 110 × 2 × 3.14 × 3600 × 10^-6
= 2.49 A
Hence, the rms value of current in the circuit is 2.49 A.

Question 5.
In Exercises 7.3 and 7.4, what is the net power absorbed by each circuit over a complete cycle. Explain your answer.
Answer:
In the inductive circuit,
rms value of current, I = 15.92 A
rms value of voltage, V = 220 V
Hence, the net power absorbed by the circuit, can be obtained by the relation,
P = VIcosΦ
where,
Φ = Phase difference between V and I.
For a pure inductive circuit, the phase difference between alternating voltage and current is 90°i. e., Φ = 90°
Hence, P = 0 i. e., the net power is zero.

In the capacitive circuit,
rms value of current, I = 2.49 A
rms value of voltage, V = 110 V
Hence, the net power absorbed by the circuit, can be obtained as
P = VIcosΦ
For a pure capacitive circuit, the phase difference between alternating voltage and current is 90°i. e., Φ = 90 °
Hence, P = 0 i. e., the net power is zero.

Question 6.
Obtain the resonant frequency ω_r of a series LCR circuit with L = 2.0 H, C = 32 μF and R = 10 Ω. What is the Q-value of this circuit?
Answer:
Resonant frequency,
ω_r = \(\frac{1}{\sqrt{L C}}\) = \(\frac{1}{\sqrt{2.0 \times 32 \times 10^{-6}}}\)
= \(\frac{1}{8}\) × 10³ = 125 rads^-1
Q = \(\frac{\omega_{r} L}{R}\) = \(\frac{125 \times 2.0}{10}\) = 25

Question 7.
A charged 30 μF capacitor is connected to a 27 mH inductor.
What is the angular frequency of free oscillations of the circuit?
Answer:
Capacitance of the capacitor, C = 30 μF = 30 × 10^-6 F,
Inductance of the inductor, L = 27 mH = 27 × 10^-3H
Angular frequency is given as
ω_r = \(\frac{1}{\sqrt{L C}}\)
= \(\frac{1}{\sqrt{27 \times 10^{-3} \times 30 \times 10^{-6}}}\)
= \(\frac{1}{9 \times 10^{-4}}=\frac{10^{4}}{9}\)
= 1.11 × 10³ rad/s
Hence, the angular frequency of free oscillations of the circuit is 1.11 × 10³ rad/s.

Question 8.
Suppose the initial charge on the capacitor in Exercise 7.7 is 6 mC. What is the total energy stored in the circuit initially? What is the total energy at later time?
Answer:
Capacitance of the capacitor, C = 30 μF = 30 × 10^-6F
Inductance of the inductor, L = 27 mH = 27 × 10^-3 H
Charge on the capacitor, Q = 6 mC = 6 × 10^-3 C
Total energy stored in the capacitor can be calculated as
E = \(\frac{1}{2} \frac{Q^{2}}{C}\) = \(\frac{1}{2} \frac{\left(6 \times 10^{-3}\right)^{2}}{\left(30 \times 10^{-6}\right)}\)
= \(\frac{36 \times 10^{-6}}{2\left(30 \times 10^{-6}\right)}\)
= \(\frac{6}{10}\) = 0.6 J
Total energy at a later time will remain the same because energy is shared between the capacitor and the inductor.

Question 9.
A series LCR circuit with R = 20 Ω, L = 1.5 H and C = 35 μF is connected to a variable frequency 200 V ac supply. When the frequency of the supply equals the natural frequency of the circuit, what is the average power transferred to the circuit in one complete cycle?
Answer:
When frequency of supply is equal to natural frequency of circuit, then resonance is obtained. At resonance X_C = X_L
⇒ Impedance, Z = \(\sqrt{R^{2}+\left(X_{C}-X_{L}\right)^{2}}\)
= R = 20Ω
Current in circuit,
I_rms = \(\frac{V_{r m s}}{R}\) = \(\frac{200}{20}\) = 10A
Power factor
cosΦ = \(\frac{R}{Z}=\frac{R}{R}\) = 1
∴ Average power p_av = V_rms I_rms cosΦ = V_rms I_rms
= 20 × 10 = 2000 W = 2 kW

Question 10.
A radio can tune over the frequency range of a portion of MW broadcast band : (800 kHz to 1200 kHz). If its LC circuit has an effective inductance of 200 μH, what must be the range of its variable capacitor?
[Hint: For timing, the natural frequency i. e., the frequency of free oscillations of the LC circuit should be equal to the frequency of the radiowave.]
Answer:
The range of frequency (v) of the radio is 800 kHz to 1200 kHz
Lower tuning frequency, v₁ = 800 kHz = 800 × 10³ Hz
Upper tuning frequency, v₂ = 1200 kHz = 1200 × 10⁶ Hz
Effective inductance of circuit, L = 200 μH = 200 × 10^-6 H
Capacitance of variable capacitor for v₁ is given as
C₁ = \(\frac{1}{\omega_{1}^{2} L}\)
where, ω₁ = Angular frequency for capacitor C₁
= 2 πv₁
= 2 π × 800 × 10³ rad/s
∴ C₁ = \(\frac{1}{\left(2 \pi \times 800 \times 10^{3}\right)^{2} \times 200 \times 10^{-6}}\)
= 197.8 × 10^-12F
= 197.8 pF
Capacitance of variable capacitor for v₂ is given as
C₂ = \(\frac{1}{\omega_{2}^{2} L}\)
where,
ω₂ = Angular frequency for capacitor C₂
= 2πv₂
= 2 π × 1200 × 10³ rad/s
∴ C ₂ = \(\frac{1}{\left(2 \pi \times 1200 \times 10^{3}\right)^{2} \times 200 \times 10^{-6}}\)
= 87.95 × 10^-12 F = 87.95 pF
Hence, the range of the variable capacitor is from 87.95 pF to 197.8 pF.

Question 11.
Figure 7.21 shows a series LCR circuit connected to a variable frequency 230 V source. Z, = 5.0H, C = 80 μF, R = 40Ω.

(a) Determine the source frequency which drives the circuit in resonance.
(b) Obtain the impedance of the circuit and the amplitude of current at the resonating frequency.
(c) Determine the rms potential drops across the three elements of the circuit. Show that the potential drop across the LC combination is zero at the resonating frequency.
Answer:
Given, the rms value of voltage V_rms = 230 V
Inductance L = 5H
Capacitance C = 80 μF = 80 × 10^-6 F
Resistance R = 40 Ω

(a) For resonance frequency of circuit
ω_r = \(\frac{1}{\sqrt{L C}}\) = \(\frac{1}{\sqrt{5 \times 80 \times 10^{-6}}}\) = 50 rad/s
Source frequency at resonance, then
v₀ = \(\frac{\omega_{0}}{2 \pi}\) = \(\frac{50}{2 \times 3.14}\) = 7.76 Hz

(b) At the resonant frequency, X_L = X_C
So, impedance of the circuit Z = R
∴ Impedance Z = 40 Ω
The rms value of current in the circuit
I_rms = \(\frac{V_{r m s}}{Z}\) = \(\frac{230}{40}\) = 5.75 A
Amplitude of current, I₀ = I_rms √2
= 5.75 × √2 = 8.13 A

(c) The rms potential drop across I,
V_L = I_rms × X_L = I_rms × ω_rL
= 5.75 × 50 × 5 = 1437.5V
The rms potential drop across R
V_R = I_rms R = 5.75 × 40 = 230 V
The rms potential drop across C,
V_C = I_rms × X_C = I_rms × \(\frac{1}{\omega_{r} C}\)
= 5.75 × \(\frac{1}{50 \times 80 \times 10^{-6}}\)
= 1437.5V
Potential drop across LC combinations
= I_rms(X_L – X_C)
= I_rms (X_L – X_L) = 0
(∵ X_L = X_C in resonance)

Question 12.
An LC circuit contains a 20 mH inductor and a 50 μF capacitor with an initial charge of 10 mC. The resistance of the circuit is negligible. Let the instant the circuit is closed be t = 0.
(a) What is the total energy stored initially? Is it conserved during LC oscillations?
(b) What is the natural frequency of the circuit?
(c) At what time is the energy stored (i) completely electrical (Lestored in the capacitor)? (ii) completely magnetic (i.e., stored in the inductor)?
(d) At what times is the total energy shared equally between the inductor and the capacitor?
(e) If a resistor is inserted in the circuit, how much energy is eventually dissipated as heat?
Answer:
Inductance of the inductor, L = 20 mH = 20 × 10^-3H
Capacitance of the capacitor, C = 50 μF = 50 × 10^-6 F
Initial charge on the capacitor, Q = 10 mC = 10 × 10^-3C

(a) Total energy stored initially in the circuit is given as
E = \(\frac{1}{2} \frac{Q^{2}}{C}\)
= \(\frac{\left(10 \times 10^{-3}\right)^{2}}{2 \times 50 \times 10^{-6}}=\frac{10^{-4}}{10^{-4}}\) = 1J
Hence, the total energy stored in the LC circuit will be conserved because there is no resistor connected in the circuit.

(b) Natural frequency of the circuit is given by the relation,
v = \(\frac{1}{2 \pi \sqrt{L C}}\)
= \(\frac{1}{2 \pi \sqrt{20 \times 10^{-3} \times 50 \times 10^{-6}}}\)
= \(\frac{10^{3}}{2 \pi}\) = 159.24 Hz
Natural angular frequency,
ω_c = \(\frac{1}{\sqrt{L C}}\) = \(\frac{1}{\sqrt{20 \times 10^{-3} \times 50 \times 10^{-6}}}\)
= \(\frac{1}{\sqrt{10^{-6}}}\) = 10³ rad/s
Hence, the natural frequency of the circuit is 10 rad/s.

(c) (i) For time period (T = \(\frac{1}{v}\) = \(\frac{1}{159.24}\) = 6.28 ms), total charge on the
capacitor at time t,
Q’ = Q cos\(\frac{2 \pi}{T}\)t
For energy stored is electrical, we can write Q’ = Q
Hence, it can be inferred that the energy stored in the capacitor is completely electrical at time, t = 0, \(\frac{T}{2}\), T, \(\frac{3 T}{2}\),…

(ii) Magnetic energy is the maximum when electrical energy, Q’ is equal to 0.
Hence, it can be inferred that the energy stored in the capacitor is
completely magnetic at time, t = \(\frac{T}{4}\), \(\frac{3 T}{4}\), \(\frac{5 T}{4}\),….

(d) Q’ = Charge on the capacitor when total energy is equally shared between the capacitor and the inductor at time t.
When total energy is equally shared between the inductor and capacitor,
the energy stored in the capacitor = \(\frac{1}{2}\) (maximum energy)

Hence, total energy is equally shared between the inductor and the capacitor at time,
t = \(\frac{T}{8}\), \(\frac{3 T}{8}\),\(\frac{5 T}{8}\)

(e) If a resistor is inserted in the circuit, then total initial energy is dissipated as heat energy in the circuit. The resistance damps out the LC oscillation.

Question 13.
A coil of inductance 0.50 H and resistance 100 Ω is connected to a 240 V, 50 Hz ac supply.
(a) What is the maximum current in the coil?
(b) What is the time lag between the voltage maximum and the current maximum?
Answer:
Given, L = 0.50 H ,R = 100 Ω, V = 240 V, v = 50 Hz
(a) Maximum (or peak) voltage V₀ = V – √2
Maximum current, I₀ = \(\frac{V_{0}}{Z}\)
Inductive reactance, X_L = ω_L = 2πvL
= 2 × 3.14 × 50 × 0.50
= 157 Ω.
Z = \(\sqrt{R^{2}+X_{L}^{2}}\)
= \(\sqrt{(100)^{2}+(157)^{2}}\) = 186 Ω

Question 14.
Obtain the answers (a) to (b) in Exercise 7.13 if the circuit is connected to a high frequency supply (240 V, 10 kHz). Hence, explain the statement that at very high frequency, an inductor in a circuit nearly amounts to an open circuit. How does an inductor behave in a dc circuit after the steady state?
Answer:
Inductance of the inductor, L = 0.5 Hz
Resistance of the resistor, R = 100 Ω
Potential of the supply voltage, V = 240 V
Frequency of the supply, v = 10 kHz = 10⁴ Hz
Angular frequency, ω = 2πv = 2 π × 10⁴ rad/s

(a) Peak voltage, V₀ = √2 × V = 240√2 V
Maximum current, I₀ = \(\frac{V_{0}}{\sqrt{R^{2}+\omega^{2} L^{2}}}\)
= \(\frac{240 \sqrt{2}}{\sqrt{(100)^{2}+\left(2 \pi \times 10^{4}\right)^{2} \times(0.50)^{2}}}\)
= 1.1 × 10^-2 A

(b) For phase difference, Φ, we have the relation
tanΦ = \(\frac{\omega L}{R}\) = \(\frac{2 \pi \times 10^{4} \times 0.5}{100}\) = 100π
Φ = 89.82° = \(\frac{89.82 \pi}{180}\) rad
ωt = \(\frac{89.82 \pi}{180}\)
t = \(\frac{89.82 \pi}{180 \times 2 \pi \times 10^{4}}\) = 25 μs

It can be observed that I₀ is very small in this case. Hence, at high frequencies, the inductor amounts to an open circuit.
In a dc circuit, after a steady state is achieved, ω = 0. Hence, inductor L behaves like a pure conducting object.

Question 15.
A 100 μF capacitor in series with a 40 Ω resistance is connected to a 110 V, 60 Hz supply.
(a) What is the maximum current in the circuit?
(b) What is the time lag between the current maximum and the voltage maximum?
Answer:
Capacitance of the capacitor, C = 100 μF = 100 × 10^-6 F = 10^-4 F
Resistance of the resistor, R = 40 Ω
Supply voltage, V = 110 V
Frequency of oscillations, v = 60 Hz
Angular frequency, co = 2πv = 2π × 60 rad/s = 120 π rad/s
For a RC circuit, we have the relation for impedance as
Z = \(\sqrt{R^{2}+\frac{1}{\omega^{2} C^{2}}}\)
peak voltage V₀ = V√2 = 110√2

(b) In an RC circuit, the voltage lags behind the current by a phase angle of Φ. This angle is given by the relation

= 1.55 × 10^-3 s
= 1.55 ms
Hence, the time lag between maximum current and maximum voltage is 1.55 ms.

Question 16.
Obtain the answers to (a) and (b) in Exercise 7.15 if the circuit is connected to a 110 V, 12 kHz supply? Hence, explain the statement that a capacitor is a conductor at very high frequencies. Compare this behaviour with that of a capacitor in a dc circuit after the steady state.
Answer:
Capacitance of the capacitor, C = 100 μF = 100 × 10^-6 F
Resistance of the resistor, R = 40 Ω
Supply voltage, V = 110 V
Frequency of the supply, v = 12 kHz = 12 × 10³ Hz
Angular frequency, ω = 2πv = 2 × π × 12 × 10³
= 24 π × 10³ rad/s
Peak voltage, V₀ = V√2 = 110 √2V

= 0.04 μs
Hence, Φ tends to become zero at high frequencies. At a high frequency, capacitor C acts as a conductor.
In a dc circuit, after the steady state is achieved, ω = 0. Hence, capacitor C acts an open circuit.

Question 17.
Keeping the source frequency equal to the resonating frequency of the series LCR circuit, if the three elements, L, C and R are arranged in parallel, show that the total current in the parallel LCR circuit is minimum at this frequency. Obtain the current rms value in each branch of the circuit for the elements and source specified in Exercise 7.11 for this frequency.
Answer:
Here, L = 5.0 H
C = 80 μF = 80 × 10^-6 F
R = 40Ω
The effective impedance of the parallel LCR is given by

Question 18.
A circuit containing a 80 mH inductor and a 60 µF capacitor in series is connected to a 230 V, 50 Hz supply. The resistance of the circuit is negligible.
(a) Obtain the current amplitude and rms values.
(b) Obtain the rms values of potential drops across each element.
(c) What is the average power transferred to the inductor?
(d) What is the average power transferred to the capacitor?
(e) What is the total average power absorbed by the circuit?
[‘Average’ implies ‘averaged over one cycle’.]
Answer:
Given,
V = 230 V, v = 50 Hz, L = 80 mH = 80 × 10^-3 H,
C = 60µF = 60 × 10^-6 F

(a) Inductive reactance X_L = ωL = 2πvL
= 2 × 3.14 × 50 × 80 × 10^-3
= 25.1 Ω

(b) RMS value of potential drops across L and C are
V_L = X_L I_rms = 25.1 × 8.23 = 207 V
V_C = X_C I_rms = 53.1 × 8.23 = 437 V
Net voltage = V_C – V_L = 230 V

(c) The voltage across L leads the current by angle \(\frac{\pi}{2}\) , therefore, average
power
P_av V_rms I_rms cos \(\frac{\pi}{2}\) = 0 (zero)

(d) The voltage across C lags behind the current by angle \(\frac{\pi}{2}\),
∴ p_av = V_rms I_rms cos \(\frac{\pi}{2}\) = 0

(e) As circuit contains pure I and pure C, average power consumed by LC circuit is zero.

Question 19.
Suppose the circuit in Exercise 7.18 has a resistance of 15 Ω. Obtain the average power transferred to each element of the circuit, and the total power absorbed.
Answer:
Here, R – 15Ω, L = 80 mH = 80 × 10^-3 H
C = 60 μF = 60 × 10^-6 F.
E_r.m.s. = 230 V
v = 50 Hz
> ω = 2πv = 2π × 50 =100 π
Z = impedance of LCR circuit
= \(\sqrt{R^{2}+\left(\omega L-\frac{1}{\omega C}\right)^{2}}\)

= 7.258 = 7.26 A
∴ Average power consumed by R or transferred to R is given by
(P_av)R = I²_r.m.s..R = (7.26)² × 15 = 790.614 W
= 791 W.
Also (P_av)_L and (P_av)_C be the average power transferred to I and C respectively.
(P_av)_L = E_r.m.s. . I_r.m.s. cosΦ
Here e.m.f. leads current by \(\frac{\pi}{2}\)
∴ (P_av)_L= E_r.m.s. . I_r.m.s. cos \(\frac{\pi}{2}\)
= 0
and (P_av )_C = = E_r.m.s. . I_r.m.s. cosΦ
= 0
( ∵ Φ = \(\frac{\pi}{2}\) and cos \(\frac{\pi}{2}\) = 0

If Pav be the total power absorbed in the circuit, then
P_av = (P_av)_L + (P_av )_C + (P_av )_R
= 0 + 0 + 791
= 791 W

Question 20.
A series LCR circuit with L = 0.12 H, C = 480 nF, R = 23 Ω is connected to a 230 V variable frequency supply.
(a) What is the source frequency for which current amplitude is maximum? Obtain this maximum value.
(b) What is the source frequency for which average power absorbed by the circuit is maximum? Obtain the value of this maximum power.
(c) For which frequencies of the source is the power transferred to the circuit half the power at resonant frequency? What is the current amplitude at these frequencies?
(d) What is the Q-factor of the given circuit?
Answer:
Inductance, L = 0.12 H
Capacitance, C = 480 nF = 480 × 10^-9 F
Resistance, R = 23 Ω
Supply voltage, V = 230 V
Peak voltage is given as V₀ = √2V
V₀ = √2 × 230 = 325.22 V

(a) Current flowing in the circuit is given by the relation,
I₀ = \(\frac{V_{0}}{\sqrt{R^{2}+\left(\omega L-\frac{1}{\omega C}\right)^{2}}}\)
where, I₀ = maximum at resonance
At resonance, we have
ω_RL – \(\frac{1}{\omega_{R} C}[latex] = 0
where, ω_R = Resonance angular frequency
∴ ω_R = [latex]\frac{1}{\sqrt{L C}}\)
= \(\frac{1}{\sqrt{0.12 \times 480 \times 10^{-9}}}\)
= \(\frac{10^{5}}{\sqrt{12 \times 48}}=\frac{10^{5}}{24}\)
= 4166.67 rad/s
∴ Resonant frequency; v_R = \(\frac{\omega_{R}}{2 \pi}\) = \(\frac{4166.67}{2 \times 3.14}\) = 663.48 HZ
and, maximum current (I₀)_max = \(\frac{V_{0}}{R}\) = \(\frac{325.22}{23}\) 14.14 A

(b) Average power absorbed by the circuit is given as
P_av = \(\frac{1}{2}\)I₀²R

The average power is maximum at ω = ω₀ at which I₀ = (I₀)_max
∴ (p_av )_max = \(\frac{1}{2}\)(I₀)²_maxR
= \(\frac{1}{2}\) × (14.14)² × 23 = 2299.3 W
= 2300 W

(c) The power transferred to the circuit is half the power at resonant frequency.
Frequencies at which power transferred is half, ω = ω_R ± Δ ω
= 2π (v_R ± Δv)
where, Δω = \(\frac{R}{2 L}\)
= \(\frac{23}{2 \times 0.12}\) = 95.83 rad/s
Hence, change in frequency, Δ v = \(\frac{1}{2 \pi}\) Δω = \(\frac{95.83}{2 \pi}\) = 15.26 Hz
Thus power absorbed is half the peak power at
v_R + Δv = 663.48 + 15.26 = 678.74 Hz
and, v_R ΔV = 663.48 – 15.26 = 648.22 Hz
Hence, at 648.22 Hz and 678.74 Hz frequencies, the power transferred is half.
At these frequencies, current amplitude can be given as
I’ = \(\frac{1}{\sqrt{2}}\) × (I₀)max = \(\frac{14.14}{\sqrt{2}}=\frac{14.14}{1.414}\) = 10 A

(d) Q-factor of the given circuit can be obtained using the relation,
Q = \(\frac{\omega_{R} L}{R}\) = \(\frac{4166.67 \times 0.12}{23}\) = 21.74
Hence, the Q-factor of the given circuit is 21.74.

Question 21.
Obtain the resonant frequency and Q-factor of a series LCR circuit with L = 3.0 H, C = 27 μF and R = 7.4 Ω. It is desired to improve the sharpness of the resonance of the circuit by reducing its ‘full width at half maximum’ by a factor of 2. Suggest a suitable way.
Answer:
Inductance, L = 3.0 H
Capacitance, C = 27 μF = 27 × 10^-6F
Resistance, R = 7.4 Ω
At resonance, resonant frequency of the source for the given LCR series circuit is given as
ω_r = \(\frac{1}{\sqrt{L C}}\) = \(\frac{1}{\sqrt{3 \times 27 \times 10^{-6}}}\)
\(\frac{10^{3}}{9}\) = 111.11 rad s^-1
Q-factor of the series
Q = \(\frac{\omega_{r} L}{R}\) = \(\frac{111.11 \times 3}{7.4}\) = 45.0446
To improve the sharpness of the resonance by reducing its ‘full width at half maximum’ by a factor of 2 without changing cor, we need to reduce R to half i. e., Resistance = \(\frac{R}{2}=\frac{7.4}{2}\) = 3.7 Ω.

Question 22.
Answer the following questions :
(a) In any ac circuit, is the applied instantaneous voltage equal to the algebraic sum of the instantaneous voltages across the series elements of the circuit? Is the same true for rms voltage?

(b) A capacitor is used in the primary circuit of an induction coil.

(c) An applied voltage signal consists of a superposition of a dc voltage and an ac voltage of high frequency. The circuit consists of an inductor and a capacitor in series. Show that the dc signal will appear across C and the ac signal across L.

(d) A choke coil in series with a lamp is connected to a dc line. The lamp is seen to shine brightly. Insertion of an iron core in the choke causes no change in the lamp’s brightness. Predict the corresponding observations if the connection is to an ac line.

(e) Why is choke coil needed in the use of fluorescent tubes with ac mains? Why can we not use an ordinary resistor instead of the choke coil?
Answer:
(a) Yes; the statement is not true for rms voltage.
It is true that in any ac circuit, the applied voltage is equal to the average sum of the instantaneous voltages across the series elements of the circuit. However, this is not true for rms voltage because voltages across different elements may not be in phase.

(b) High induced voltage is used to charge the capacitor.
A capacitor is used in the primary circuit of an induction coil. This is because when the circuit is broken, a high induced voltage is used to charge the capacitor to avoid sparks.

(c) The dc signal will appear across capacitor C because for dc signals, the impedance of an inductor (L) is negligible while the impedance of a capacitor (C) is very high (almost infinite). Hence, a dc signal appears across C. For an ac signal of high frequency, the impedance of L is high and that of C is very low. Hence, an ac signal of high frequency appears across L.

(d) If an iron core is inserted in the choke coil (which is in series with a lamp connected to the ac line), then the lamp will glow dimly. This is because the choke coil and the iron core increase the impedance of the circuit.

(e) A choke coil is needed in the use of fluorescent tubes with ac mains because it reduces the voltage across the tube without wasting much power. An ordinary resistor cannot be used instead of a choke coil for this purpose because it wastes power in the form of heat.

Question 23.
A power transmission line feeds input power at 2300 V to a stepdown transformer with its primary windings having 4000 turns. What should be the number of turns in the secondary in order to get output power at 230 V?
Answer:
Input voltage, V₁ = 2300 V
Number of turns in primary coil, n₁ = 4000
Output voltage, V₂ = 230 V
Number of turns in secondary coil = n₂
Voltage is related to the number of turns as
\(\frac{V_{1}}{V_{2}}=\frac{n_{1}}{n_{2}}\)
\(\frac{2300}{230}=\frac{4000}{n_{2}}\)
n₂ = \(\frac{4000 \times 230}{2300}\) = 400
Hence, there are 400 turns in the second winding.

Question 24.
At a hydroelectric power plant, the water pressure head is at a height of 300 m and the water flow available is 100 m³s^-1 . If the turbine generator efficiency is 60%, estimate the electric power available from the plant (g = 9.8 ms^-2).
Answer:
Height of the water pressure head, h = 300 m
Volume of water flow per second, V = 100 m³/s
Efficiency of turbine generator, η = 60% = 0.6
Acceleration due to gravity, g = 9.8 m/ s²
Density of water, ρ = 10³ kg/m³
Electric power available from the plant = η × h ρ gV
= 0.6 × 300 × 10³ × 9.8 × 100
= 176.4 × 10⁶ W
= 176.4 MW

Question 25.
A small town with a demand of 800 kW of electric power at 220 V is situated 15 km away from an electric plant generating power at 440 V. The resistance of the two wire line carrying power is 0.5 Ω per km. The town gets power from the line through a 4000-220 V step-down transformer at a sub-station in the town.
(a) Estimate the line power loss in the form of heat.
(b) How much power must the plant supply, assuming there is negligible power loss due to leakage?
(c) Characterise the step up transformer at the plant.
Answer:
Total electric power required, P = 800 kW = 800 × 10³ W
Supply voltage, V = 220 V
Voltage at which electric plant is generating power, V’ = 440 V
Distance between the town and power generating station, d = 15 km
Resistance of the two wire lines carrying power = 0.5 Ω/km
Total resistance of the wires, R = (15 + 15)0.5 = 15Ω
A step-down transformer of rating 4000 – 220 V is used in the sub-station.
Input voltage, V₁ = 4000 V
Output voltage, V₂ = 220 V
rms current in the wire lines is given as
I = \(\frac{P}{V_{1}}\) = \(\frac{800 \times 10^{3}}{4000}\) = 200 A

(a) Line power loss = I²R = (200)² × 15 = 600 × 10³ W = 600 kW

(b) Assuming that the power loss is negligible due to the leakage of the current.
Total power supplied by the plant = 800 kW + 600 kW = 1400 kW

(c) Voltage drop in the power line = IR = 200 × 15 = 3000 V
Hence, total voltage transmitted from the plant = 3000 + 4000 = 7000 V Also, the power generated is 440 V.
Hence, the rating of the step-up transformer situated at the power plant is 440 V – 7000 V.

Question 26.
Do the same exercise as above with the replacement of the earlier transformer by a 40,000-220 V step-down transformer (Neglect, as before, leakage losses though this may not be a good assumption any longer because of the very high voltage transmission involved). Hence, explain why high voltage transmission is preffered?
Answer:
The rating of the step-down transformer is 40000 V – 220 V
Input voltage, V₁ = 40000 V
Output voltage, V₂ = 220 V
Total electric power required, P = 800 kW = 800 × 10³ W
Source potential, V = 220 V
Voltage at which the electric plant generates power, V’ = 440 V
Distance between the town and power generating station, d = 15 km
Resistance of the two wire lines carrying power = 0.5 Ω/km
Total resistance of the wire lines, R = (15 + 15)0.5 = 15 Ω
rms current in the wire line is given as
I = \(\frac{P}{V_{1}}\) = \(\frac{800 \times 10^{3}}{40000}\) = 20A

(a) Line power loss = I²R
= (20)² × 15 = 6000 W = 6 kW

(b) Assuming that the power loss is negligible due to the leakage of current.
Hence, total power supplied by the plant = 800 kW + 6 kW = 806 kW

(c) Voltage drop in the power line = 7R = 20 × 15 = 300 V
Hence, voltage that is transmitted by the power plant
= 300 + 40000 = 40300 V
The power is being generated in the plant at 440 V.
Hence, the rating of the step-up transformer needed at the plant is 440 V – 40300 V. ‘
Hence, power loss during transmission = \(\frac{600}{1400}\) x 100 = 42.8%
In the previous exercise, the power loss due to the same reason is
\(\frac{6}{800}\) × 100 = 0.744%
Since the power loss is less for a high voltage transmission, high voltage transmissions are preferred for this purpose.

Punjab State Board PSEB 12th Class Chemistry Important Questions Chapter 9 Coordination Compounds Important Questions and Answers.

PSEB 12th Class Chemistry Important Questions Chapter 9 Coordination Compounds

Very Short Answer Type Questions

Question 1.
Why is CO a stronger ligand than Cl^– ?
Answer:
CO forms π bonds so it is a stronger ligand than Cl^–.

Question 2.
What is the relationship between observed colour of the complex and the wavelength of light absorbed by the complex?
Answer:
When white light falls on the complex, some part of it is absorbed. Higher the crystal field splitting, lower will be the wavelength absorbed by the complex. The observed colour of complex is the colour generated from the wavelength left over.

Question 3.
How many isomers are there for octahedral complex [CoCl₂ (en) (NH₃)₂]⁺?
Answer:
There will be three isomers: cis and trans isomers. Cis will also show optical isomerism.

Question 4.
Why are low spin tetrahedral complexes not formed?
Answer:
Because for tetrahedral complexes, the crystal field stabilisation energy is lower than pairing energy.

Question 5.
A complex of the type [M(AA)₂X₂]ⁿ⁺ is known to be optically active. What does this indicate about the structure of the complex? Give one example of such complex.
Answer:
An optically active complex of the type [M(AA)₂X₂]ⁿ⁺ indicates cis- octahedral structure, e.g., cis-[Pt(en)₂Cl₂]²⁺ or cis-[Cr(en)₂Cl₂]⁺.

Question 6.
Why is the complex [Co(en)₃]³⁺ more stable than the complex [CoF₆]^3-?
Answer:
Due to chelate effect as the complex [Co(en)₃]³⁺ contains chelating ligand \(\ddot{\mathrm{NH}}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\ddot{\mathrm{NH}}_{2}\).

Question 7.
What do you understand by ‘denticity of a ligand’?
Answer:
The number of coordinating groups present in ligand is called the denticity of ligand. For example, denticity of ethane-1, 2-diamine is 2, as it has two donor nitrogen atoms which can link to central metal atom.

Question 8.
What type of isomerism is shown by the complex [CO(NH₃)₅(SCN)]²⁺?
Answer:
Linkage isomerism.

Question 9.
Arrange the following complex ions in increasing order of crystal field splitting energy △₀ :
[Cr(Cl)₆]^3-, [Cr(CN)₆]^3-, [Cr(NH₃)₆]³⁺
Answer:
[Cr(Cl)₆]^3- < [Cr(NH₃)₆]³⁺ < [Cr(CN)₆]^3-

Question 10.
A coordination compound with molecular formula CrCl₃.4H₂O precipitates one mole of AgCl with AgNO₃ solution. Its molar conductivity is found to be equivalent to two ions. What is the structural formula and name of the compound?
Answer:
[Cr(H₂O)₄Cl₂] Cl
[Tetraaquadichloridochromium (III) chloride]

Short Answer Type Questions

Question 1.
Give the electronic configuration of the following complexes on the basis of crystal field splitting theory.
[CoF₆]^3-, [Fe(CN)₆]^4- and [Cu(NH₃)₆]²⁺
Answer:
[CoF₆]^3-: Co³⁺(d⁶) \(t_{2 g}^{4} e_{g}^{2}\)
[Fe(CN)₆]^4- : Fe²⁺ (d⁶) \(t_{2 g}^{6} e_{g}^{0}\)
[Cu(NH₃)₆]²⁺ : Cu²⁺ (d⁹) \(t_{2 g}^{6} e_{g}^{3}\)

Question 2.
(i) What type of isomerism is shown by [Co(NH₃) ₅ONO]Cl₂?
(ii) On the basis of crystal field theory, write the electronic configuration for d⁴ ion, if △₀ < P.
(iii) Write the hybridisation and shape of [Fe(CN)₆]^3-.
(Atomic number of Fe = 26)
Answer:
(i) Linkage isomerism and the linkage isomer is [Co(NH₃) ₅ONO]Cl₂.
(ii) If △₀ < P, the fourth electron enters one of two e_g orbitals giving the configuration \(t_{2 g}^{3} e_{g}^{1}\).
(iii) Fe³⁺ : 3d⁵ 4s⁰

Question 3.
Explain why [Fe(H₂O)₆]³⁺ 5.92 BM whereas [Fe(CN)₆]^3- has a value of only 1.74 BM.
Answer:
[Fe(CN)₆]^3- involves d²sp³ hybridisation with one unpaired electron and [Fe(H₂O)₆]³⁺ involves sp³d² hybridisation with five unpaired electrons. This difference is due to the presence of strong CN^– and weak ligand H₂O in these complexes.

Question 4.
CuSO₄∙5H₂O is blue in colour while CuSO₄ is colourless. Why?
Answer:
In CuSO₄∙5H₂O, water acts as ligand as a result it causes crystal field splitting. Hence, d-d transition is possible in CuSO₄∙5H₂O and shows colour. In the anhydrous CuSO₄ due to the absence of water (ligand), crystal field splitting is not possible and hence it is colourless.

Question 5.
Why do compounds having similar geometry have different magnetic moment?
Answer:
It is due to the presence of weak and strong ligands in complexes, if CFSE is high, the complex will show low value of magnetic moment and vice versa, e.g., [CoF₆]^3- and [Co(NH₃)₆]³⁺, the former is paramagnetic and the latter is diamagnetic.

Question 6.
A metal ion Mⁿ⁺ having d⁴ valence electronic configuration combines with three bidentate ligands to form a complex compound. Assuming △₀ > P:
(i) Write the electronic configuration of d⁴ ion.
(ii) What type of hybridisation will Mⁿ⁺ ion has?
(iii) Name the type of isomerism exhibited by this complex.
Answer:
(i) \(t_{2 g}^{4} e_{g}^{0}\)
(ii) sp³d²
(iii) Optical isomerism

Long Answer Type Questions

Question 1.
Using crystal field theory, draw energy level diagram, write electronic configuration of the central metal atom/ion and determine the magnetic moment value in the following: [COF₆]^3-, [CO(H₂O)₆]²⁺, [CO(CN)₆]³
Answer:
Magnetic moment, μ = \(\sqrt{n(n+2)}\)
Where, n = Number of unpaired electrons

No unpaired electrons, so it is diamagnetic.

Question 2.
(i) Draw the geometrical isomers of complex [Pt(NH₃)₂Cl₂].
(ii) Write the hybridisation and magnetic behaviour of the complex [Ni(CO)₄].
(Atomic no. of Ni = 28)
Answer:

Geometrical isomers of [Pt(NH₃)₂Cl₂]

(ii) The complex [Ni(CO)₄] involves sp³ hybridisation.

The complex is diamagnetic as evident from the absence of unpaired electrons.

Punjab State Board Syllabus PSEB 12th Class Political Science Book Solutions Guide Pdf in English Medium and Punjabi Medium are part of PSEB Solutions for Class 12.

PSEB 12th Class Political Science Guide | Political Science Guide for Class 12 PSEB

Political Science Guide for Class 12 PSEB | PSEB 12th Class Political Science Book Solutions

PSEB 12th Class Political Science Book Solutions in English Medium

12th Class Political Science Guide PSEB Part A Political Theory

• Chapter 1 Political System
• Chapter 2 Liberalism
• Chapter 3 Marxism
• Chapter 4 Political Ideas of Mahatma Gandhi
• Chapter 5 Bureaucracy (Civil Services)
• Chapter 6 Public Opinion
• Chapter 7 Party System
• Chapter 8 Interest and Pressure Groups

Political Science Guide for Class 12 PSEB Part B Indian Political System

• Chapter 9 Indian Democracy: Problems and Challenges
• Chapter 10 Democracy at Grassroots
• Chapter 11 Party System in India
• Chapter 12 Electoral System
• Chapter 13 National Integration
• Chapter 14 Foreign Policy of India-Determinants and Basic Principles
• Chapter 15 India and United Nations
• Chapter 16 India and SAARC
• Chapter 17 India and Her Neighbours-Nepal, Sri Lanka, China, Bangladesh and Pakistan
• Chapter 18 India’s Relations with USA and Russia
• Chapter 19 India’s Approach to Major World Issues

PSEB 12th Class Political Science Book Solutions in Hindi Medium

• Chapter 1 राजनीतिक व्यवस्था
• Chapter 2 तुलनात्मक राजनीति
• Chapter 3 राजनीतिक संस्कृति
• Chapter 4 राजनीतिक समाजीकरण
• Chapter 5 उदारवाद
• Chapter 6 मार्क्सवाद
• Chapter 7 महात्मा गान्धी के राजनीतिक विचार
• Chapter 8 नौकरशाही
• Chapter 9 निर्वाचक
• Chapter 10 जनमत
• Chapter 11 दल प्रणाली
• Chapter 12 हित तथा दबाव समूह
• Chapter 13 भारतीय लोकतन्त्र
• Chapter 14 स्थानीय स्तर पर लोकतन्त्र
• Chapter 15 भारत में दलीय प्रणाली
• Chapter 16 चुनाव व्यवस्था
• Chapter 17 राष्ट्रीय एकीकरण
• Chapter 18 भारत की विदेश नीति-निर्धारक तत्त्व एवं मूलभूत सिद्धान्त
• Chapter 19 भारत तथा संयुक्त राष्ट्र संघ
• Chapter 20 भारत और सार्क
• Chapter 21 भारत एवं उसके पड़ोसी देश : नेपाल, श्रीलंका, चीन, बंगलादेश एवं पाकिस्तान
• Chapter 22 भारत के अमेरिका एवं रूस से सम्बन्ध
• Chapter 23 विश्व के प्रमुख विषयों के प्रति भारत का दृष्टिकोण

PSEB 12th Class Political Science Syllabus

Part – A Political Theory

Unit I: Political System
(i) Meaning, Characteristics
(ii) Functions of Political System
(iii) David Easton’s input-output model
(iv) Difference between state and political system.

Unit II: Some major contemporary Political Theories
(i) Liberalism
(ii) Marxism
(iii) Political ideas of Mahatma Gandhi

Unit III: Bureaucracy (Civil Services)
(i) Meaning and importance
(ii) Recruitment
(iii) Role and functions
(iv) Distinction between Political Executive and Permanent Executive and their respective roles
Public opinion
(i) Role and importance of Public Opinion in a Democratic Polity.
(ii) Agencies for the formulation and expression of Public Opinion.

Unit IV: Party System
(i) Political parties – their functions and importance
(ii) Basis of formation of Political Parties
(iii) Types of Party System
(iv) The Role of Opposition
Interest and Pressure Groups
(i) Interest Groups and Pressure Groups – their nature, types, and functions
(ii) Ways of functioning of pressure groups

Part – B Indian Political System

Unit V: Indian Democracy
(i) Parliamentary Model
(ii) Problems and challenges to Indian Democracy & Future of Indian democracy
Democracy at Grassroot
(i) Concept of Panchayati Raj
(ii) Structure and Working of Panchayati Raj (73th Amendment)
(iii) Panchayati Raj-Some problems
(iv) Local Bodies in Urban Areas (74th Amendment)

Unit VI: Party System in India
(i) Nature of Party System in India
(ii) Study of major 4 national political parties (INC, BJP, CPI. CPI (M) their programs and policies. Regional Political Parties in Punjab (SAD, AAP)
(iii) Problems facing the Indian Party System
Electoral System
(i) Adult Franchise Direct and Indirect Elections And People’s Participation
(ii) Voting behaviour – meaning and determinants
(iii) Election Commission and Election Procedure

Unit VII: National Integration
(i) Problems of National Integration
(ii) Steps taken to promote National Integration
Foreign Policy of India
(i) Determinants of Foreign Policy
(ii) Basic principles of Foreign Policy
(iii) India and the United Nations, India, and SAARC

Unit VIII: India and the World
(i) India’s relations with her Neighbours: Nepal, Sri Lanka, China, Bangladesh and Pakistan
(ii) India’s relations with U.S.A. and Russia
(iii) India’s approach to major world issues: Human Rights, Disarmament and Globalization.

Punjab State Board PSEB 12th Class Chemistry Important Questions Chapter 11 Alcohols, Phenols and Ethers Important Questions and Answers.

PSEB 12th Class Chemistry Important Questions Chapter 11 Alcohols, Phenols and Ethers

Very Short Answer Type Questions

Question 1.
Write the structures of the products when Butan-2-ol reacts with the following:
(i) CrO₃
(ii) SOCl₂
Answer:

Question 2.
What happens when ethanol reacts with CH₃COCl/pyridine ?
Answer:

Question 3.
When phenol is created with bromine water, while precipitate is obtained. Prove the structure and the name of the compound formed.
Answer:
When phenol is treated with bromine water, white ppt. of 2, 4, 6-tribromophenol is obtained.

Question 4.
Answer the following questions :
(i) Dipole moment of phenol is smaller than that of methanol. Why?
(ii) In Kolbe’s reaction, instead of phenol, phenoxide ion is treated with carbon dioxide. Why ?
Answer:
(i) In phenol, C—O bond is less polar due to electron-withdrawing effect of benzene ring whereas in methanol, C—O bond is more polar due to electron-releasing effect of —CH₃ group.

(ii) Phenoxide ion is more reactive than phenol towards electrophilic aromatic substitution and hence undergoes electrophilic substitution with carbon dioxide which is a weak electrophile.

Question 5.
What is denatured alcohol ?
Answer:
Alcohol is made unfit for drinking by mixing some copper sulphate and pyridine in it. This is called denatured alcohol.

Question 6.
Arrange the following compounds in the increasing order of their acidic strength: p-cresol, p -nitrophenol, phenol
Answer:
p-cresol < phenol < p-nitrophenol

Question 7.
Arrange the following compounds in decreasing order of acidity.
(i) H₂O, ROH, HC ☰ CH
(ii)
(iii) CH₃OH, H₂O, C₆H₆OH
Answer:
(i) H₂O > ROH > HC ☰ CH
(ii)
(iii) C₆H₅OH > H₂O > CH₃OH

Question 8.
Suggest a reagent for conversion of ethanol to ethanal.
Answer:
Ethanol can be oxidises into ethanal by using pyridinium chlorochromate.

Question 9.
Explain why sodium metal can be used for drying diethyl ether but not ethyl alcohol.
Answer:
Due to presence of an active hydrogen atom, ethyl alcohol reacts with sodium metal.
2CH₃ — CH₂ — OH + 2Na → 2CH₃ — CH₂ — ONa + H₂
Diethyl ether, on the other hand, does not have replaceable hydrogen atom therefore does not react with sodium metal hence can be dried by metallic sodium.

Question 10.
Phenol is an acid but does not react with sodium bicarbonate solution. Why?
Answer:
Phenol is a weaker acid than carbonic acid (H₂CO₃) and hence does not liberate CO₂from sodium bicarbonate.

Question 11.
In the process of wine making, ripened grapes are crushed so that sugar and enzyme should come in contact with each other and fermentation should start. What will happen if anaerobic conditions are not maintained during this process?
Answer:
Ethanol will be converted into ethanoic acid.

Short Answer Type Questions

Question 1.
Why is the reactivity of all the three classes of alcohols with cone. HCl and ZnCl₂ (Lucas reagent) different ?
Answer:
The reaction of alcohols with Lucas reagent (cone. HCl and ZnCl₂) follow S_N1 mechanism. S_N1 mechanism depends upon the stability of carbocations (intermediate). More stable the intermediate carbocation, more reactive is the alcohol.

Tertiary carbocations are most stable among the three classes of carbocations and the order of the stability of carbocation is 3° > 2° > 1°. This order, intum, reflects the order of reactivity of three classes of alcohols i. e., 3° > 2° > 1°.

Thus , as the stability of carbocations are different so the reactivity of all the three classes of alcohols with Lucas reagent is different.

Question 2.
Write the mechanism of the following reaction:

Answer:
S_N2 mechanism

Question 3.
Explain a process in which a biocatalyst is used in industrial preparation of a compound known to you.
Answer:
Enzymes are biocatalyst. These biocatalysts (enzymes) are used in the industrial preparation of ethanol. Ethanol is prepared by the fermentation of molasses—a dark brown coloured syrup left after crystallisation of sugar which still contains about 40% of sugar.

The process of fermentation actually involves breaking down of large molecules into simple ones in the presence of enzymes. The source of these enzymes is yeast. The various reactions taking place during fermentation of carbohydrates are :

In wine making, grapes are the source of sugars and yeast. As grapes ripen, the quantity of sugar increases and yeast grows on the outer skin. When grapes are crushed, sugar and the enzyme come in contact and fermentation starts. Fermentation takes place in anaerobic conditions i.e., in absence of air. CO₂ gas is released during fermentation.

The action of zymase is inhibited once the percentage of alcohol ,formed exceeds 14 per cent. If air gets into fermentation mixture, the oxygen of air oxidises ethanol to ethanoic acid which in turn destroys the taste of alcoholic drinks.

Question 4.
Explain why alcohols and ethers of comparable molecular mass have different boiling points ?
Answer:
Boiling point depends upon the strength of intermolecular forces of attraction. Higher these forces of attraction, more will be the boiling point. Alcohols undergo intermolecular hydrogen bonding. So, the molecules of alcohols are held together by strong intermolecular forces of attraction.

But in ethers no hydrogen atom is bonded to oxygen. Therefore, ethers are held together by weak dipole-dipole forces, not by strong hydrogen bond.

Since, lesser amount of energy is required than to break weak dipole-dipole forces in ethers than to break strong hydrogen bonds in alcohol.

Question 5.
Explain why is O ＝ C ＝ O non-polar while R—O—R is polar ?
Answer:
CO₂ is a linear molecule. The dipole moment of two C —O bonds are equal and opposite and they cancel each other and hence the dipole moment of CO₂ is zero and it is a non-polar molecule.

While for ethers, two dipoles are pointing in the same direction. These two dipoles do not cancel the effect of each other. Therefore, there is a finite resultant dipoles and hence R—O—R is a polar molecule.

Question 6.
Give reasons for the following:
(i) p-Nitrophenol is more acidic than o-nitrophenol
(ii) Bond angle C—O—C in ethers is slightly higher than the tetrahedral angle (109°28′).
(iii) (CH₃)₃C—Br on reaction with NaOCH₃ gives an alkene instead of an ether.
Answer:
(i)
Intramolecular H-bonding in o-nitrophenol makes loss of proton difficult. Therefore, p-nitrophenol is more acidic than o-nitrophenol.

(ii) The bond angle in ether is slightly higher than 109 °28′ due to repulsive interaction between the two bulky alkyl groups.

(iii) It is because NaOCH₃ is a strong nucleophile as well as a strong base. Thus, elimination reaction predominates over substitution reaction.

Question 7.
Explain the following behaviours :
(i) Alcohols are more soluble in water than the hydrocarbons of comparable molecular masses.
(ii) Ortho-nitrophenol is more acidic than ortho-methoxyphenol.
(iii) Cumene is a better starting material for the preparation of phenol.
Answer:
(i) Alcohols are more soluble in water than the hydrocarbons of comparable molecular masses because of H-bond formation between alcohol and water molecules.
(ii) Ortho-nitrophenol is more acidic than ortho-methoxyphenol because nitro being the electron with drawing group stabilises the phenoxids ion.
(iii) Cumene is a better starting material for the preparation of phenol because side product formed in this reaction is acetone which is another important organic compound.

Long Answer Type Questions

Question 1.
(a) Name the starting material used in the industrial preparation of phenol.
(b) Write complete reaction for the bromination of phenol in aqueous and non-aqueous medium.
(c) Explain why Lewis acid is not required in bromination of phenol?
Answer:
(a) The starting material used in the industrial preparation of phenol is cumene.

(b) Phenols when treated with bromine water gives polyhalogen derivatives in which all the hydrogen atoms present at ortho and para positions with respect to —OH group are replaced by bromine atoms.

However, in non-aqueous medium such as CS₂, CCl₄, CHCl₃ monobromophenols are obtained.

In aqueous solution, phenol ionises to form phenoxide ion. This ion activates the benzene ring to a very large extent and hence the substitution of halogen takes place at all three positions.

On the other hand, in non-aqueous solution ionisation of phenol is greatly suppressed. Therefore, ring is activated slightly and hence monosubstitution occur.

(c) Lewis acid is an electron deficient molecule. In bromination of benzene, Lewis acid is used-to polarise Br₂ to form Br+ electrophile.

In case of phenol, oxygen atom of phenol itself polarises the bromine molecule to form Br+ ion (electrophile). So, Lewis acid is not required in the bromination of phenol.

Question 2.
Explain the mechanism of the following reactions :
(i) Addition of Grignard’s reagent to the carbonyl group of a compound forming an adduct followed by hydrolysis.
(ii) Acid catalysed dehydration of an alcohol forming an alkene.
(iii) Acid catalysed hydration of an alkene forming an alcohol.
Answer:
(i) Step I : Nucleophilic addition of Grignard reagent to carbonyl group.

Step II : Formation of carbocation : It is the slowest step and hence, the rate determining step.

To drive the equilibrium to the right, ethylene is removed as it is formed.

Punjab State Board PSEB 12th Class Chemistry Book Solutions Chapter 4 Chemical Kinetics Textbook Exercise Questions and Answers.

PSEB Solutions for Class 12 Chemistry Chapter 4 Chemical Kinetics

PSEB 12th Class Chemistry Guide Chemical Kinetics InText Questions and Answers

Question 1.
From the rate expression for the following reactions, determine their order of reaction and the dimensions of the rate constants.
(i) 3 NO(g) → N₂O(g) Rate = k[NO]²
(ii) H₂O₂ (aq) +3I^– (aq) + 2H⁺ → 2H₂O (l) + \(\mathbf{I}_{3}^{-}\)
Rate = k[H₂O₂] [I^–]
(iii) CH₃CHO(g) → CH₄(g) + CO(g) Rate = k [CH₃CHO]^3/2
(iv) C₂H₅Cl(g) → C₂H₄(g) + HCl (g) Rate = k [C₂H₅Cl]
Solution:
(i) Given, rate = k [NO]²
Therefore, order of the reaction = 2
Dimension of rate constant (k) = \(\frac{\text { Rate }}{[\mathrm{NO}]^{2}}\)
= \(\frac{m o l L^{-1} s^{-1}}{\left(m o l L^{-1}\right)^{2}}\)
= \(\frac{\mathrm{mol} \mathrm{L}^{-1} \mathrm{~s}^{-1}}{\mathrm{~mol}^{2} \mathrm{~L}^{-2}}\)
= L mol^-1 s^-1

(ii) Given, rate = k [H₂O₂] [I^– ]
Therefore, order of the reaction = 2
Dimension of k = \(\frac{\text { Rate }}{\left[\mathrm{H}_{2} \mathrm{O}_{2}\right]\left[\mathrm{I}^{-}\right]}\)
= \(\frac{\mathrm{mol} \mathrm{L}^{-1} \mathrm{~s}^{-1}}{\left(\mathrm{~mol} \mathrm{~L}^{-1}\right)\left(\mathrm{mol} \mathrm{L}^{-1}\right)}\)
= L mol^-1 s^-1

(iii) Given rate = k[CH₃CHO]^3/2
Therefore, order of the reaction = \(\frac{3}{2}\)
Dimension of k = \(\frac{\text { Rate }}{\left[\mathrm{CH}_{3} \mathrm{CHO}\right]^{3 / 2}}\)

= \(\frac{\text { mol L }^{-1} \mathrm{~s}^{-1}}{\mathrm{~mol}^{\frac{3}{2}} \mathrm{~L}^{-\frac{3}{2}}}\)
= mol ^-1/2L^1/2 s^-1

(iv) Given, rate = k [C₂H₅Cl]
Therefore, order of the reaction = 1
Dimension of k = \(\frac{\text { Rate }}{\left[\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{Cl}\right]}\)
= \(\frac{\mathrm{mol} \mathrm{L}^{-1} \mathrm{~s}^{-1}}{\mathrm{~mol} \mathrm{~L}^{-1}}\) = s^-1

Question 2.
For the reaction:
2A + B → A₂B
the rate = k[A] [B]² with k = 2.0 x 10^-6 mol^-2L²s^-1. Calculate the initial rate of the reaction when [A] = 0.1 mol L^-1, [B] = 0.2 mol L^-1. Calculate the rate of reaction after [A] is reduced to 0.06 mol L^-1.
Solution:
The initial rate of the reaction is
Rate = k [A][B]²
= (2.0 × 10^-6 mol^-2 L² s^-1) (0.1 mol L^-11) (0.2 mol L^-1 )²
= 8.0 × 10^-9 mol L^-1 s^-1
When [A] is reduced from 0.1 mol L^-1 to 0.06 molL^-1, the concentration of A reacted = (0.1 – 0.06) mol L^-1 = 0.04 mol L^-1 Therefore, concentration of B reacted
= \(\frac{1}{2}\) × 0.04 mol L^-1 = 0.02 mol L^-1
Then, concentration of B available, [B] = (0.2 -0.02) mol L^-1
= 0.18 mol L^-1
After [A] is reduced to 0.06 mol L^-1, the rate of the reaction is given by,
Rate = k [A][B]²
= (2.0 × 10^-6 mol^-2 L² s^-1) (0.06 mol L^-1) (0.18 mol L^-1)²
= 3.89 × 10^-9 mol L^-1 s^-1

Question 3.
The decomposition of NH₃ on platinum surface is zero order reaction. What are the rates of production of N₂ and H₂ if k = 2.5 x 10^-4 mol^-1 L s^-1?
Solution:
The decomposition of NH₃ on platinum surface is represented by the following equation

For zero order reaction, rate = k
∴ \(-\frac{1}{2} \frac{d\left[\mathrm{NH}_{3}\right]}{d t}=\frac{d\left[\mathrm{~N}_{2}\right]}{d t}=\frac{1}{3} \frac{d\left[\mathrm{H}_{2}\right]}{d t}\)
= 2.5 × 10^-4 mol L^-1 s^-1
Therefore, the rate of production of N₂
\(\frac{d\left[\mathrm{~N}_{2}\right]}{d t}\) = 2.5 × 10^-4 mol L^-1 s^-1
The rate of production of H₂
\(\frac{d\left[\mathrm{H}_{2}\right]}{d t}\) = 3 × 2.5 × 10^-4 mol L^-1 s^-1
= 7.5 × 10^-4 mol L^-1 s^-1

Question 4.
The decomposition of dimethyl ether leads to the formation of CH₄, H₂ and CO and the reaction rate is given by
Rate = k [CH₃OCH₃]^3/2
The rate of reaction is followed by increase in pressure in a closed vessel, so the rate can also be expressed in terms of the partial pressure of dimethyl ether, i.e.,
Rate = k(PCH_3OCH3 )^3/2
If the pressure is measured in bar and time in minutes, then what are the units of rate and rate constants?
Solution:
If the pressure is measured in bar and time in minutes, then
Unit of rate = bar min^-1
Rate = k(PCH_3OCH3 )^3/2
⇒ k = \(\frac{\text { Rate }}{\left(p_{\mathrm{CH}_{3} \mathrm{OCH}_{3}}\right)^{3 / 2}}\)
=

Question 5.
Mention the factors that affect the rate of a chemical reaction.
Answer:
The factors that affect the rate of a chemical reaction are as follows :
(i) Nature of reactants: Ionic substances react more rapidly than covalent compounds because ions produced after dissociation are immediately available for reaction.

(ii) Concentration of reactants: Rate of a chemical reaction is direcdy proportional to the concentration of reactants.

(iii) Temperature: Generally rate of a reaction increases on increasing the temperature.

(iv) Presence of catalyst: In presence of catalyst, the rate of reaction generally increase and the equilibrium state is attained quickly in reversible reactions.

(v) Surface area of the reactants: Rate of reaction increases with increase in surface area of the reactants. That is why powdered form of reactants is preffered than their granular form.

Question 6.
A reaction is second order with respect to a reactant. How is the rate of reaction affected if the concentration of the reactant is (i) doubled (ii) reduced to half?
Solution:
Let the concentration of the reactant be [A] = a
Rate of reaction, R = k [A]² = ka²
(i) If the concentration of the reactant is doubled, i.e. [A] = 2a, then the rate of the reaction would be
R’ = k (2a)²
= 4ka² = 4R
Therefore, the rate of the reaction would increase by 4 times.

Question 7.
What is the effect of temperature on the rate constant of a reaction? How can this effect of temperature on rate constant be represented quantitatively?
Answer:
The rate constant is nearly doubled with a rise in temperature by 10° for a chemical reaction.

The temperature effect on the rate constant can be represented quantitatively by Arrhenius equation, k = Ae^-E_a/RT

Where, k is the rate constant, A is the Arrhenius factor or the frequency factor, R is the gas constant, T is the temperature, and E_a is the energy of activation for the reaction.

Question 8.
In a pseudo first order hydrolysis of ester in water, the following results were obtained:

t/s	0	30	60	90
[Ester]/molL-1	0.55	0.31	0.17	0.085

(i) Calculate the average rate of reaction between the time interval 30 to 60 seconds.
(ii) Calculate the pseudo first order rate constant for the hydrolysis of ester.
Solution:
(i) Average rate of reaction between the time interval, 30 to 60 seconds
= \(\frac{d[\text { Ester }]}{d t}\)
= \(\frac{0.31-0.17}{60-30}\)
= \(\frac{0.14}{30}\)
= 4.67 × 10^-3 mol L^-1 s^-1

Question 9.
A reaction is first order in A and second order in B.
(i) Write the differential rate equation.
(ii) How is the rate affected on increasing the concentration of B three times?
(iii) How is the rate affected when the concentrations of both A and B are doubled?
Solution:
(i) The differential rate equation will be
– \(\frac{d[\mathrm{R}]}{d t}\) = k[A][B]²

(ii) If the concentration of B is increased three times, then
– \(\frac{d[\mathrm{R}]}{d t}\) = k[A][3B]²
= 9.k [A][B]²
Therefore, the rate of reaction will increase 9 times.

(iii) When the concentrations of both A and B are doubled,
– \(\frac{d[\mathrm{R}]}{d t}\) = k[2A][2B]²
= 8.k [A] [B]²
Therefore, the rate of reaction will increase 8 times.

Question 10.
In a reaction between A and B, the initial rate of reaction (r₀) was measured for different initial concentrations of A and B as given below:

A/mol L-1	0.20	0.20	0.40
B/mol L-1	0.30	0.10	0.05
r0/mol L-1 s-1	5.07 × 10-5	5.07 × 105	1.43 × 10-4

What is the order of the reaction with respect to A and B?
Solution:
Let the order of the reaction with respect to A be x and with respect to B be y.
Therefore
r₀ = k [A]^x [B]^y
5.07 × 10^-5 = k[0.20]^x [0.30]^y …………. (i)
5.07 × 10^-5 = k[0.20]^x [0.10]^y …………. (ii)
1.43 × 10^-4 = k[0.40]^x [0.05]^y ……….. (iii)

Hence, the order of the reaction with respect to A is 1.5 and with respect to B is 0.

Question 11.
The following results have been obtained during the kinetic studies of the reaction:
2A + B → C + D

Determine the rate law and the rate constant for the reaction.
Solution:
Let the order of the-reaction with respect to A be x and with respect to B be y.
Therefore, rate of the reaction is given by,
Rate = k [A]^x [B]^y According to the question,
6.0 × 10^-3; = k[0.1]^x [0.1]^y …………. (i)
7.2 × 10^-2 = k[0.3]^x [0.2]^y …………… (ii)
2.88 × 10^-1 = k[0.3]^x [0.4]^y ………….. (iii)
2.40 × 10^-2 = k[0.4]^x [0.1]^y …………… (iv)
Dividing equation (iv) by (i), we get

Question 12.
The reaction between A and B is first order with respect to A and zero order with respect to B. Fill in the blanks in the following table:

Solution:
The given reaction is of the first order with respect to A and of zero order with respect to B.
Therefore, the rate of the reaction is given by,
Rate = k[A]¹[B]⁰
⇒ Rate = fc[A]
From experiment I, we get
2.0 × 10^-2 molL^-1 min^-1 = k(0.1 molL^-1)
⇒ k = 0.2 min^-1

From experiment II, we get
4.0 × 10^-2 molL^-1 min^-1 = 0.2 min^-1 [A]
⇒ [A] = 0.2 mol L^-1

From experiment III, we get
Rate = 0.2 min^-1; × 0.4 mol L^-1
= 0.08 mol L^-1 min^-1

From experiment IV, we get
2.0 × 10^-2 molL^-1 min^-1 = 0.2 min^-1 [A]
⇒ [A] = 0.1 mol L^-1

Question 13.
Calculate the half-life of a first order reaction from their rate constants given below:
(i) 200 s^-1
(ii) 2 min^-1
(iii) 4 years^-1
Solution:
Half life period for first order reaction, t_1/2 = \(\)
(i) t_1/2 = \(\frac{0.693}{200 \mathrm{~s}^{-1}}\) = 0.347 × 10^-2 s
= 3.47 × 10^-3 s
(ii) t_1/2 = \(\frac{0.693}{2 \min ^{-1}}\) = 0.35 mm
(iii) t_1/2 = \(\frac{0.693}{4 \text { years }^{-1}}\)= 0.173 years 4 years-1

Question 14.
The half-life for radioactive decay of ¹⁴C is 5730 years. An archaeological artifact containing wood had only 80% of the ¹⁴C found in a living tree. Estimate the age of the sample.
Solution:
Decay constant (k) = \(\frac{0.693}{t_{1 / 2}}\)
\(\frac{0.693}{5730}\) = years ^-1
Radioactive decay follows first order kinetics
t = \(\frac{2.303}{k}\) = log\(\frac{[R]_{0}}{[R]}\)
= \(\frac{\frac{2.303}{0.693}}{5730}\) × log \(\frac{100}{80}\)
= 1845 years
Hence, the age of the sample is 1845 years.

Question 15.
The experimental data for decomposition of N₂0₅
[2N₂O₅ → 4NO₂ + O₂]
in gas phase at 318K are given below:

(i) Plot [N₂O₅] against t.
(ii) Find the half-life period for the reaction.
(iii) Draw a graph between log [N₂O₅ ] and t.
(iv) What is the rate law?
(v) Calculate the rate constant
(vi) Calculate the half-life period from k and compare it with (ii).
Solution:
(i) The plot of [N₂O₅] against time is given below:

(ii) Initial concentration of N₂O₅ = 1.63 x 10^-2 M
Half of this concentration = 0.815 x 10^-2 M
Time corresponding to this concentration = 1440 s
Hence t_1/2 = 1440 s

(iii) For graph between log[N₂O₅] and time, we first find the values of log[N₂O₅]

Time (s)	102 × [N2O5] mol L-1	log [N2O5]
0	1.63	-1.79
400	1.36	-1.87
800	1.14	-1.94
1200	0.93	-2.03
1600	0.78	-2.11
2000	0.64	-2.19
2400	0.53	-2.28
2800	0.43	-2.37
3200	0.35	-2.46

(iv) The given reaction is of the first order as the plot, log [N₂0₅] v/s t, is a straight line. Therefore, the rate law of the reaction is
Rate = k [N₂O₅]

(v) From the plot, log [N₂O₅] v/s t, we get
Slope = \(\frac{-2.46-(-1.79)}{3200-0}\)
= \(\frac{-0.67}{3200}\)
Again, slope of the line of the plot log [N₂O₅] v/s t is given by
– \(\frac{k}{2.303}\)
Therefore we get
\(-\frac{k}{2.303}=-\frac{0.67}{3200}\)
k = \(\frac{0.67 \times 2.303}{3200}\)
= 4.82 × 10^-4s^-1

(vi) Half-life period (t_1/2) = \(\)
= \(\frac{0.693}{4.82 \times 10^{-4} \mathrm{~s}^{-1}}\) = 1438 s
Half-life period (t_1/2) is calculated from the formula and slopes are approximately the same.

Question 16.
The rate constant for a first order reaction is 60 s^-1. How much time will it take to reduce the initial concentration of the reactant to its 1/16^th value?
Solution:
For first order reaction
t = \(\frac{2.303}{k}\) log \(\frac{1}{(a-x)}\) …………. (i)
Given (a – x) = \(\frac{1}{16}\); k= 60 s^-1
Placing the values in equation (i)
t = \(\frac{2.303}{60 \mathrm{~s}^{-1}}\) log \(\frac{a \times 16}{a}\)
= \(\frac{2.303}{60 \mathrm{~s}^{-1}}\) log16 \(\frac{2.303}{60 \mathrm{~s}^{-1}}\) × 4 log 2
= \(\frac{2.303}{60 \mathrm{~s}^{-1}}\) × 4 × 0.3010
= 4.6 × 10^-2s
Hence, the required time is 4.6 × 10^-2 s.

Question 17.
During nuclear explosion, one of the products is ⁹⁰Sr with half-life of 28.1 years. If 1μ g of ⁹⁰Sr was absorbed in the bones of a newly born baby instead of calcium, how much of it will remain after 10 years and 60 years if it is not lost metabolically.
Solution:
As radioactive disintegration follows first order kinetics,
∴ Decay constant of ⁹⁰Sr, k = \(\frac{0.693}{t_{1 / 2}}\)
= \(\frac{0.693}{28.1 \mathrm{y}}\) = 2.466 × 10^-2y^-1

To calculate the amount left after 10 years
[R]₀ = 1μg, t = 10 years, k = 2.466 × 10^-2y^-1,[R] =?
k = \(\frac{2.303}{t}\) log \(\frac{[R]_{0}}{[R]}\)
2.466 × 10^-2 = \(\frac{2.303}{10}\) log \(\frac{1}{[R]}\)
or log[R] = – 0.1071
or [Rl = Antilog \(\overline{1}\).8929 = 0.78 14 μg

To calculate the amount left after 60 years
2.466 × 10^-2 = \(\frac{2.303}{60}\) log \(\frac{1}{[R]}\)
or log[R] = – 0.6425
or [R] = Antilog \(\overline{1}\).3575 = 0.2278 μg

Question 18.
For a first order reaction, show that time required for 99% completion is twice the time required for the completion of 90% of reaction.
Solution:
For a first order reaction, the time required for 99% completion is

Therefore, t₁ = 2t₂
Hence, the time required for 99% completion of a first order reaction is twice the time required for the completion of 90% of the reaction.

Question 19.
A first order reaction takes 40 min for 30% decomposition.
Calculate t_1/2
Solution:
Given, t = 40 min,
For a first order reaction,

Question 20.
For the decomposition of azoisopropane to hexane and nitrogen at 543 K, the following data are obtained.

t (sec)	P(mm of Hg)
0	35.0
360	54.0
720	63.0

Calculate the rate constant.
Solution:
The decomposition of azoisopropane to hexane and nitrogen at 543 K is represented by the following equation:

Hence, the average value of rate constant
k = \(\frac{\left(2.175 \times 10^{-3}\right)+\left(2.235 \times 10^{-3}\right)}{2} s^{-1}\)
= 2.21 × 10^-3s^-1

Question 21.
The following data were obtained during the first order thermal decomposition of SO₂Cl₂ at a constant volume.
SO₂Cl₂(g) → SO₂(g) + Cl₂(g)

Experiment	Time/s-1	Total pressure/atm
1	0	0.5
2	100	0.6

Calculate the rate of the reaction when total pressure is 0.65 atm.
Solution:
The first order thermal decomposition of SO₂cl₂ at a constant volume is represented by the following equation:

= 2.23 × 10^-3s^-1

When P_t = 0.65 atm,
P₀ + p = 0.65
⇒ p = 0.65 – P₀
= 0.65 – 0.5
= 0.15 atm
Pressure of SO₂Cl₂ at time t (P_SO2Cl2 SO₂Cl₂
= P₀ – P
= 0.5 – 0.15
= 0.35 atm

Therefore, the rate of equation, when total pressure is 0.65 atm, is given by,
Rate = k × (P_SO2Cl2 SO₂Cl₂)
= (2.23 × 10^-3 s^-1) (0.35 atm)
= 7.8 × 10^-5 atm s^-1

Question 22.
The rate constant for the decomposition of N₂O₅ at various temperatures is given below:

Draw a graph between In k and 1/T and calculate the values of A and E_a.
Predict the rate constant at 30° and 50°C.
Solution:
To draw the plot of log k versus 1/T, we can rewrite the given data as follows:

From graph, we find
Slope = \(\frac{-2.4}{0.00047}\) = 5106.38
E_a = – Slope × 2.303 × R
= – (- 5106.38) × 2.303 × 8.314
= 97772.58 J mol^-1
= 97.77258 kJ mol^-1

We know that,
log k = log A – \(\frac{E_{a}}{2.303 R T}\)
log k = log \(\left[-\frac{E_{a}}{2.303 R}\right] \frac{1}{T}\) = log A
Compare it with y = mx + c (which is equation of line in intercept form)
log A = value of intercept on y-axis i.e.
on log k-axis [y₂ – y₁ = -1 – (-7.2)]
= (-1 + 7.2) = 6.2 ,
log A = 6.2
A = Antilog 6.2
= 1.585 × 10⁶ s^-1
The values of rate constant k can be found from graph as follows:

We can also calculate the value of A from the following formula
log k = log A = \(\frac{E_{a}}{2.303 R T}\)

Question 23.
The rate constant for the decomposition of hydrocarbons is 2.418 × 10^-5 s^-1 at 546 K. If the energy of activation is 179.9 kJ/mol, what will be the value of pre-exponential factor.
Solution:
Given, k = 2.418 × 10^-5s^-1, T = 546 K
E_a = 179.9 kJ mol^-1 = 179.9 × 10³ J mol^-1
According to the Arrhenius equation,
k = Ae^-Ea/RT
ln k = ln A – \(\frac{E_{a}}{R T}\)
log k = log A – \(\frac{E_{a}}{2.303 R T}\)
log A = log K + \(\frac{E_{a}}{2.303 R T}\)
= log(2.418 × 10¹⁵s^-1) + \(\frac{179.9 \times 10^{3} \mathrm{~J} \mathrm{~mol}^{-1}}{2.303 \times 8.314 \mathrm{Jk}^{-1} \mathrm{~mol}^{-1} \times 546 \mathrm{~K}}\)
= (0.3835 – 5) +17.2082 = 12.5917
Therefore, A = antilog (12.5917) = 3.9 × 10¹²s^-1

Question 24.
Consider a certain reaction A → Products with k = 2.0 × 10^-2s^-1 Calculate the concentration of A remaining after 100 s if the initial concentration of A is 1.0 mol L^-1.
Solution:
Given, k = 2.0 x 10^-2s^-1, t = 100 s, [A]₀ = 1.0 mol L^-1
Since, the unit of k is s^-1, the given reaction is a first order reaction.

Question 25.
Sucrose decomposes in acid solution into glucose and fructose according to the first order rate law, with t_1/2 =3.00 hours. What fraction of sample of sucrose remains after 8 hours?
Solution:
For a first order reaction,

= 0.158 M
Hence, the fraction of sample of sucrose that remains after 8 hours is 0.158 M.

Question 26.
The decomposition of hydrocarbon follows the equation k = (45 × 10¹¹ s¹)e^-28000k/T
Calculate E_a.
Solution:
The given equation is
k = (45 × 10¹¹ s¹)e^-28000k/T …(i)
Arrhenius equation is given by,
k = Ae^E_a/RT …(ii)
From equation (i) and (ii), we get
\(\frac{E_{a}}{R T}\) = \(\frac{28000 \mathrm{~K}}{T}\)
⇒ E_a = R × 28000 K
= 8.314 J K^-1 mol^-1 × 28000 K
= 232792 J mol^-1
= 232.792 kJ mol^-1

Question 27.
The rate constant for the first order decomposition of H₂O₂ is given by the following equation :
log k = 14.34 – 1.25 × 10⁴ K/T
Calculate E_a for this reaction and at what temperature will its half-period be 256 minutes?
Solution:
Arrhenius equation is given by,
k = Ae^-E_a/RT
⇒ log k = log A – \(\frac{E_{a}}{2.303 \mathrm{RT}}\) …(i)
log k = 14.34 – 1.25 × 10⁴ K/T …(ii)
From equation (i) and (ii), we get
\(\frac{E_{a}}{2.303 \mathrm{RT}}\) = \(\frac{1.25 \times 10^{4} \mathrm{~K}}{T}\)
⇒ E_a = 1.25 × 10⁴K × 2.303 × R
= 1.25 × 10⁴K × 2.303 × 8.314 J K^-1 mol^-1
= 239339.3 J mol^-1
= 239.34 kJ mol^-1
Also, when t_1/2 = 256 minutes,
For first order reaction
k = \(\frac{0.693}{t_{1 / 2}}\)
= \(\frac{0.693}{256}\)
= 2.707 × 10^-13 min^-1
= 4.51 × 10^-5 s^-1
According to Arrhenius theory,
log k = 14.34 – 1.25 × 10^,4K/T

Question 28.
The decomposition of A into product has value of & as 45 × 10³ s^-1 at 10°C and energy of activation 60 kJ mol^-1. At what temperature would k be 1.5 × 10⁴ s^-1.
Solution:
From Arrhenius equation, we get
\(\log \frac{k_{2}}{k_{1}}\) = \(\frac{E_{a}}{2.303 \mathrm{R}}\left(\frac{T_{2}-T_{1}}{T_{1} T_{2}}\right)\)
Also, k₁ = 4.5 × 10³ s^-1
T₁ = 273 + 10 = 283k
k₂ = 1.5 × 10⁴ s^-1
E_a = 60 kJmol^-1 = 6.0 × 10⁴ Jmol^-1

⇒ 0.0472T₂ = T₂ – 283
⇒ 0.9528T₂ = 283
⇒ T₂ = 297.019 K
= 297K = (297 – 273)⁰C
= 24⁰C
Hence, k would be 1.5 × 10⁴ s^-1 at 24⁰C.

Question 29.
The time required for 10% completion of a first order reaction at 298 K is equal to that required for its 25% completion at 308 K. If the value of A is 4 × 10¹⁰ s^-1. Calculate k at 318 K and E_a.
Solution:
For a first order reaction,

To calculate k at 318 K,
It is given that, A = 4 × 10¹⁰ s^-1, T = 318 K
Again, from Arrhenius equation, we get
log k = log A – \(\frac{E_{a}}{2.303 \mathrm{RT}}\)
= log (4 × 10¹⁰) – \(\frac{76.64 \times 10^{3}}{2.303 \times 8.314 \times 318}\)
= (0.6021 + 10) – 12.5870 = -1.9849 k
k = Antilog (-1.9849)
= Antilog (2.0151) = 1.035 × 10^-2s^-1
E_a = 76.640 kJ mol^-1
E_a = 76.640 kJmol^-1
k = 1.035 × 10^-2s^-1

Question 30.
The rate of a reaction quadruples when the temperature changes from 293 K to 313 K. Calculate the energy of activation of the reaction assuming that it does not change with temperature.
Solution:
Given, k₂ = 4k₁, T₁ = 293 K, T₂ = 313 K
From Arrhenius equation, we get

Hence, the required energy of activation is 52.86 kJ mol^-1

Chemistry Guide for Class 12 PSEB Chemical Kinetics Textbook Questions and Answers

Question 1.
For the reaction R → P, the concentration of a reactant changes from 0.03 M to 0.02 M in 25 minutes. Calculate the average rate of reaction using units of time both in minutes and seconds.
Solution:

Question 2.
In a reaction, 2A → Products, the concentration of A decreases from 0.5 mol L^-1 to 0.4 mol L^-1 in 10 minutes. Calculate the rate during this interval?
Solution:
Rate of reaction = Rate of disappearance of A = – \(\frac{1}{2} \frac{\Delta[A]}{\Delta t}\)
= – \(\frac{1}{2} \frac{[A]_{2}-[A]_{1}}{t_{2}-t_{1}}\)
= – \(\frac{1}{2} \frac{(0.4-0.5) \mathrm{mol} \mathrm{L}^{-1}}{10 \mathrm{~min}}\)
= – \(\frac{1}{2} \frac{-0.1}{10}\)
= 0.005 mol L^-1 min^-1
= 5 × 10^-3 M min^-1

Question 3.
For a reaction, A + B → Product; the rate law is given by,
r = k [A]^1/2 [B]². What is the order of the reaction?
Solution:
The order of the reaction = \(\frac{1}{2}\) + 2
= 2\(\frac{1}{2}\) = 2.5

Question 4.
The conversion of molecules X to Y follows second order kinetics. If concentration of X is increased to three times how will it affect the rate of formation of Y? ‘
Solution:
The reaction X → Y follows second order kinetics.
Therefore, the rate equation for this reaction will be:
Rate (r) = k[X]² = k × X² …………. (i)
If the concentration of X is increased to three times, then
Rate (r’) = fc(3X)² = k × 9X² ………….. (ii)
Dividing eq. (ii) by eq. (i)
\(\frac{r^{\prime}}{r}=\frac{k \times 9 X^{2}}{k \times X^{2}}\) = 9
It means that the rate of formation of Y will increase by nine times.

Question 5.
A first order reaction has a rate constant 1.15 × 10^-3s^-1. How long will 5 g of this reactant take to reduce to 3 g?
Solution:
Initial amount [R]₀ = 5 g
Final amount [R] = 3 g
Rate constant (k) = 1.15 × 10^-3s^-1
We know that for a 1^st order reaction,

= 444.38 s
= 444 s

Question 6.
Time required to decompose SO₂Cl₂ to half of its initial amount is 60 minutes. If the decomposition is a first order reaction, calculate the rate constant of the reaction.
Solution:
We know that for a 1^st order reaction,
t_1/2 = \(\frac{0.693}{k}\)
> k = \(\frac{0.693}{t_{1 / 2}}\)
= \(\frac{0.693}{60 \mathrm{~min}}\) = \(\frac{0.693}{(60 \times 60) \mathrm{s}}\)
or k = 1.925 × 10^-4 s^-1]

Question 7.
What will be the effect of temperature on rate constant?
Answer:
The rate constant of a reaction is nearly doubled with a 10° rise in temperature. However, the exact dependence of the rate of a chemical reaction on temperature is given by Arrhenius equation,
k = Ae^-Ea/RT
Where, A is the Arrhenius factor or the frequency factor, T is the temperature, R is the gas constant, E_a is the activation energy.

Question 8.
The rate of the chemical reaction doubles for an increase of 10 K in absolute temperature from 298 K. Calculate E_a.
Solution:
Given, T₁ = 298 K
∴ T₂ = (298 + 10)K = 308K
We also know that the rate of the reaction doubles when temperature is increased by 10°.
Therefore, let us take the value of k₁ = k and that of k₂ = 2k
Also, R =8.314 JK^-1 mol^-1
Now, substituting these values in the equation:

Question 9.
The activation energy for the reaction
2HI (g) → H₂ + I₂(g)
is 209.5 kJ mol^-1 at 58IK. Calculate the fraction of molecules of reactants having energy equal to or greater than activation energy?
Solution:
Fraction of molecules of reactants (x) having energy equal to or greater than activation energy may be calculated as follows
or log x = \(\frac{-E_{a}}{R T}\) or log x = –\(\frac{E_{a}}{2.303 R T}\)
or log x = – \(\frac{209.5 \times 10^{3}}{2.303 \times 8.314 \times 581}\)
= -18.8323
x = Antilog (-18.8323) = Antilog (\(\overline{19}\).1677)
= 1.471 × 10^-19
Hence, fraction of molecules of reactants having energy equal to or greater than activation energy = 1.471 × 10^-19