Question

Chromium plating can involve the electrolysis of an electrolyte of an acidified mixture of chromic acid and chromium sulphate. If during electrolysis the substance being plated increases in mass by$2.6g$ and $0.6$ dm${}^3$ of oxygen are evolved at an inert anode, the oxidation state of chromium ions being discharged must be: (atomic mass of Cr $=$ 52 and 1 mole of gas at room temperature and pressure occupies a volume of 24 dm${}^3$)

• A. $-1$
• B. $0$
• C. $+1$
• D. $+2$

Answer 1

The correct option is D $+2$

As same charge is passed through both electrode so same no of equivalent wiil be used.
Eq. of Cr $=$ Eq. of oxygen
$\frac{26}{52/n}=\frac{0.6\times 4}{14}$
$\therefore n=2$