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By passing a fixed current through molten salts for two hours, 40 kg of calcium is deposited. Using the identical current for the same two-hour interval, how much aluminium would be liberated? (Atomic masses: Ca = 40, Al = 27)

1. 22 kg
2. 18 kg
3. 9 kg
4. 27 kg

Correct answer: 18 kg

Solution

Equal charge deposits equal gram-equivalents. Equivalents of Ca = 40000/(40/2) = 2000. So equivalents of Al = 2000 too. Mass of Al = equivalents * (27/3) = 2000 * 9 = 18000 g = 18 kg.

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