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Electrochemistry · Question 29

JEE Main 2025 (Online) 3rd April Evening ShiftMCQMedium📈 Topic in 6% papers+4−1
1

The standard cell potential ( E cell ) of a fuel cell based on the oxidation of methanol in air that has been used to power television relay station is measured as 1.21 V. The standard half cell reduction potential for O2 ( E O2/H2O ) is 1.229 V. Choose the correct statement :

  1. Reactants are fed at one go to each electrode.
  2. Oxygen is formed at the anode.
  3. The standard half cell reduction potential for the reduction of CO2 ( E CO2/CH3OH ) is 19 mV
  4. Reduction of methanol takes place at the cathode.

Answer

(3) The standard half cell reduction potential for the reduction of CO2 ( E CO2/CH3OH ) is 19 mV

Solution

Anode (oxidation): CH3OH + H2O CO2 + 6H+ + 6e-

Cathode (reduction): 32O2 + 6H+ + 6e- 3H2O

E cell = E O2/H2O - E CO2/CH3OH

1.21 = 1.229 - E CO2/CH3OH

E CO2/CH3OH = 0.019 V = 19 mV (3) is correct.

(1) In a fuel cell, reactants are fed continuously to the electrodes. Incorrect.

(2) Oxygen is consumed (reduced) at the cathode, not formed at the anode. Incorrect.

(4) Methanol is oxidised at the anode. Incorrect.

Answer: (3)

JEE Main 2025 (Online) 3rd April Evening Shift

Keep practising — Electrochemistry

2

40 mL of a mixture of CH3COOH and HCl (aqueous solution) is titrated against 0.1 M NaOH solution conductometrically. Which of the following statement is correct? [figure]

  1. The concentration of CH3COOH in the original mixture is 0.005 M
  2. The concentration of HCl in the original mixture is 0.005 M
  3. CH3COOH is neutralised first followed by neutralisation of HCl
  4. Point 'C' indicates the complete neutralisation of HCl
JEE Main 2025 (Online) 3rd April Evening Shift
3

Consider the following electrochemical cell at standard condition. Au(s) | QH2, Q | NH4X(0.01 M) || Ag+(1 M) | Ag(s) Ecell = +0.4 V The couple QH2/Q represents quinhydrone electrode, the half cell reaction is given below: [figure] [Given : E0 Ag+/Ag = +0.8 V and 2.303RTF = 0.06 V] The pKb value of the ammonium halide salt (NH4X) used here is . (nearest integer)

JEE Main 2025 (Online) 2nd April Morning Shift
4

0.2\% (w/v) solution of NaOH is measured to have resistivity 870.0 m m. The molar conductivity of the solution will be 102 mS dm2 mol-1. (Nearest integer)

JEE Main 2025 (Online) 2nd April Evening Shift
5

For a Mg | Mg2+(aq) || Ag+(aq) | Ag the correct Nernst Equation is :

  1. Ecell = E cell - RT2F [Ag+]2[Mg2+]
  2. Ecell = E cell - RT2F [Mg2+][Ag+]
  3. Ecell = E cell - RT2F [Ag+][Mg2+]
  4. Ecell = E cell + RT2F [Ag+]2[Mg2+]
JEE Main 2025 (Online) 29th January Morning Shift
6

The molar conductivity of a weak electrolyte when plotted against the square root of its concentration, which of the following is expected to be observed?

  1. Molar conductivity increases sharply with increase in concentration.
  2. Molar conductivity decreases sharply with increase in concentration.
  3. A small increase in molar conductivity is observed at infinite dilution.
  4. A small decrease in molar conductivity is observed at infinite dilution.
JEE Main 2025 (Online) 29th January Morning Shift
7

Given below is the plot of the molar conductivity vs concentration for KCl in aqueous solution. [figure] If, for the higher concentration of KCl solution, the resistance of the conductivity cell is 100 , then the resistance of the same cell with the dilute solution is 'x' . The value of x is (Nearest integer)

JEE Main 2025 (Online) 28th January Morning Shift
8

Electrolysis of 600 mL aqueous solution of NaCl for 5 min changes the pH of the solution to 12. The current in Amperes used for the given electrolysis is . (Nearest integer).

JEE Main 2025 (Online) 28th January Evening Shift

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