Arrange the following in increasing order of the mass of the metal deposited when 1 amp of current is passed through their electrolytic solutions for 1 minute.
(A). Al (atomic mass = $27\, g\, mol^{-1}$)
(B). Mg (atomic mass = $24\, g\, mol^{-1}$)
(C). Ag (atomic mass = $108\, g\, mol^{-1}$)
(D). Cu (atomic mass = $63.5\, g\, mol^{-1}$)
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A), (B), (D), (C)
According to Faraday’s laws of electrolysis, the mass of metal deposited is proportional to its equivalent weight (M / n).
Let’s calculate $\frac{M}{n}$ for each metal:
- (A) Al³⁺ → $\frac{27}{3} = 9$
- (B) Mg²⁺ → $\frac{24}{2} = 12$
- (D) Cu²⁺ → $\frac{63.5}{2} = 31.75$
- (C) Ag⁺ → $\frac{108}{1} = 108$
Increasing order of mass deposited:
$\text{Al} < \text{Mg} < \text{Cu} < \text{Ag}$