Q.1. The molar conductance of NaCl, HCI, and CH3COONa at infinite dilution are 126.45, 426.16, and 91.0 S cm mol-1 respectively. The molar conductance of CH3COOH at infinite dilution is. Choose the right option for your answer. (2021)
(a) 698.28 ohm-1 cm2 mol-1
(b) 540.48 ohm-1 cm2 mol-1
(c) 201.28 ohm-1 cm2 mol-1
(d) 390.71 ohm-1 cm2 mol-1
Ans: D
We know that molar conductance of CH3COOH
=
= 91 + 426.16 - 126.45
= 390.71 ohm-1 cm2 mol-1
Q.2. The molar conductivity of 0.007 M acetic acid is 20 S cm2 mol-1. What is the dissociation constant of acetic acid? Choose the correct option. (2021)
(a) 1.75 × 10–5 mol L–1
(b) 2.50 × 10–5 mol L–1
(c) 1.75 × 10–4 mol L–1
(d) 2.50 × 10–4 mol L–1
Ans: A
Q.3. Hydrolysis of sucrose is given by the following reaction. (2020)
Sucrose + H2O ⇌ Glucose + Fructose
If the equilibrium constant (Kc) is 2 × 1013 at 300 K, the value of ΔrGº at the same temperature will be:
A: 8.314 J mol-1 K-1 × 300 K × ln(3 × 1013)
B: -8.314 J mol-1 K-1 × 300 K × ln(4 × 1013)
C: -8.314 J mol-1 K-1 × 300 K × ln(2 × 1013)
D: 8.314 J mol-1 K-1 × 300 K × ln(2 × 1013)
Ans: C
ΔG°= -RT ln K
⇒ ΔG° = -8.314 J mol-1 K-1 × 300 K-1 × ln (2 × 1013)
Q.4. On electrolysis of dil. sulphuric acid using platinum (Pt) electrode, the product obtained at the anode will be: (2020)
A: H2S gas
B: SO2 gas
C: Hydrogen gas
D: Oxygen gas
Ans: D
Anode : 2H2O → O2 + 4H+ + 4e-
Cathode : 2H+ + 2e- → H2(g)
∴ oxygen gas will be obtained at anode.
Q.5. The number of Faradays (F) required to produce 20g of calcium from molten CaCl2 (Atomic mass of Ca = 40 g mol-1) is: (2020)
A: 3
B: 4
C: 1
D: 2
Ans: C
Q.6. For a cell involving one electron E°cell = 0.59 V at 298 K, the equilibrium constant for the cell reaction is : (2019)
A: 1.0 × 102
B: 1.0 × 105
C: 1.0 × 1010
D: 1.0 × 1030
Ans: C
(At equilibrium, Q = Keq and Ecell = 0) (from equation (i))
Q.7. For the cell reaction at 298 K. The standard Gibbs energy
of the cell reaction is :[Given that Faraday constant F = 96500 C mol–1] (2019)
A: – 46.32 kJ mol–1
B: – 23.16 kJ mol–1
C: 46.32 kJ mol–1
D: 23.16 kJ mol–1
Ans: A
= – 2 × 96500 × 0.24 J mol–1
= – 46320 J mol–1
= – 46.32 kJ mol–1
Q.8. Consider the change in the oxidation state of Bromine corresponding to different emf values as shown in the diagram below:
Then the species undergoing disproportionation is:- (2018)
A: BrO3-
B: BrO4-
C: Br2
D: HBrO
Ans: D
Calculate E°cell corresponding to each compound undergoing disproportionation reaction. The reaction for which E°cell comes out +ve is spontaneous.
Q.9. (2017)
A: E1 < E2
B: E1 > E2
C: E2 = 0 ≠ E1
D: E1 = E2
Ans: B
Q.10. The pressure of H2 required to make the potential of H2-electrode zero in pure water at 298 K is : (2016)
A: 10-4 atm
B: 10-14 atm
C: 10-12 atm
D: 10-10 atm
Ans: B
pH = 7 for water.
Q.11. A device that converts the energy of combustion of fuels like hydrogen and methane, directly into electrical energy is known as (2015)
A: Ni-Cd cell
B: Fuel Cell
C: Electrolytic Cell
D: Dynamo
Ans: B
In fuel cell energy of combustion is converted into electrical energy.
Q.12. When 0.1 mol is oxidised the quantity of electricity required to completely oxidise
is : (2014)
A: 9650 C
B: 96.50 C
C: 96500 C
D: 2 × 96500 C
Ans: A
The oxidation reaction is
Q.13. The weight of silver (at. wt. = 108) displaced by a quantity of electricity that displaces 5600 mL of O2 at STP will be : (2014)
A: 54.0 g
B: 108.0 g
C: 5.4 g
D: 10.8 g
Ans: B
According to Faraday's second law,
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