NEET Previous Year Questions (2014-21): Electrochemistry Notes | Study Chemistry Class 12 - NEET

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 (K_c) is 2 × 10¹³ at 300 K, the value of Δ_rGº 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 = K_eq and E_cell = 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,