JEE Main · 2025 · 22 Jan 2025 · Shift 1 · Redox Reactions and Electrochemistry

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A solution of aluminium chloride is electrolysed for 30 minutes using a current of 2 A. The amount of the aluminium deposited at the cathode is ______.
[Given : molar mass of aluminium and chlorine are

27 g mol^{- 1}

and

35.5 g mol^{- 1}

respectively, Faraday constant

= 96500 C mol^{- 1}

(A)1.660 g
(B)1.007 g
(C)0.336 g✓ Correct
(D)0.441 g

Answer: (C)

Solution

Aluminium deposits at the cathode by the three-electron reduction

A l^{3 +} + 3 e^{-} \to A l

, so its equivalent mass is

27/3 = 9

g/equiv.

Charge passed:

Q = I t = 2 \times (30 \times 60) = 3600

C

By Faraday's first law:

w = \frac{Q}{96500} \times E = \frac{3600}{96500} \times 9 = 0.336 g

The mass of aluminium deposited at the cathode is 0.336 g.

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JEE Main · 2025 · 22 Jan 2025 · Shift 1 · Redox Reactions and Electrochemistry

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