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Electrochemistry is the… (Class 12 Chemistry 2026, Q30)

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ChemistryCBSE Class 12 · Board exam 2026, set 56/5/1 · 4 marks · Case-based

CBSE Class 12 Chemistry 2026: question 30

Set in the CBSE Class 12 board exam of 2026, paper 56/5/1, section D, question 30, for 4 marks. Try it first; the hints and our step-by-step solution are below.

Q30 · 4 marks · Case-basedCompetency-basedElectrochemistry

Electrochemistry is the study of the relationship between chemical energy and electrical energy. Many spontaneously occurring chemical reactions liberate electrical energy. In electrolysis, electrical energy is converted directly into chemical energy. The product of an electrolytic reaction depends on the nature of the material being electrolysed and the type of electrode used. Oxidising and reducing species present in the electrolytic cell and their standard electrode potential too, affect the products of electrolysis. Electrolysis plays an important role in most people’s daily lives, whether it is for the manufacturing of aluminium, electroplating of metals, or the synthesis of chemical compounds.

Michael Faraday was the first scientist who proposed two laws to explain the quantitative aspects of electrolysis, popularly known as Faraday’s laws of electrolysis. Faraday’s laws of electrolysis provide a basis for mathematical analysis of the mass deposited at electrodes and the amount of charge passed through them.

Faraday’s laws are fundamental in various applications, including electroplating, metal extraction, battery technology and chemical synthesis. These laws also help in environmental monitoring and in various chemistry experiments.

Answer the following questions :

  1. (a)

    Predict the products of electrolysis in each of the following :
    (i) An aqueous solution of with platinum electrodes.
    (ii) A concentrated solution of with platinum electrodes.

    2 marks
  2. (b)(i)

    How much charge in faraday is required for the reduction of 1 mol of to Ag ?

    1 mark

  3. OR

    (b)(ii)

    State Faraday’s second law of electrolysis.

    1 mark
  4. (c)

    The following reactions occur at the anode during the electrolysis of aqueous sodium chloride solution :

    = 1·36 V (I)

    = 1·23 V (II)

    Which reaction is feasible at the anode and why ?

    1 mark

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 56/5/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

In each cell, decide which species is more easily reduced at the cathode and which is oxidised at the anode; in concentrated H₂SO₄ sulphate is oxidised.

Hint 2

The number of faradays equals the number of moles of electrons. For (c), think about why O₂ evolution is slower than its E° suggests.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. (a)(i) Aqueous CuCl₂ with Pt electrodes:

    • Anode: chlorine,
    • Cathode: copper,
    1 mark

  2. (a)(ii) Concentrated H₂SO₄ with Pt electrodes:

    • Anode: peroxodisulphate ion,
    • Cathode: hydrogen gas,
    1 mark

  3. (b)(i) . One mole of electrons is needed, so the charge is 1 F (96487 C).

    1 mark

  4. (b)(ii) (Alternative) Faraday's second law: when the same quantity of electricity is passed through solutions of different electrolytes, the amounts of the substances liberated at the electrodes are proportional to their chemical equivalent weights.

  5. (c) Reaction (I), liberation of Cl₂, actually takes place at the anode. Reaction (II) has the lower E° value, but it is kinetically slow because of the overpotential of oxygen.

    1 mark

Answer: (a)(i) Anode Cl₂, cathode Cu; (ii) anode S₂O₈²⁻, cathode H₂; (b)(i) 1 F; (b)(ii) Faraday's second law; (c) Reaction (I), due to overpotential of O₂

Where the marks are

  • (a)(i) Cl₂ at anode (½ mark), Cu at cathode (½ mark)
  • (a)(ii) S₂O₈²⁻ at anode (½ mark), H₂ at cathode (½ mark)
  • (b)(i) 1 F (1 mark) OR (b)(ii) correct statement of the second law (1 mark)
  • (c) Reaction (I) (½ mark), overpotential of oxygen (½ mark)

Revise the chapter

Practise this chapterBoard-style questions from Electrochemistry, one at a time, marked against the answer key and marking points.Back to the full paper2026 board paper, set 56/5/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.