Question

Equivalent mass of $H_{3}P{O}_2$ when it disproportionates into $P{H}_3$ and $H_{2}P{O}_3$ is:

(Molecular mass $=M$)

• A. $M$
• B. $\frac{M}{2}$
• C. $\frac{M}{4}$
• D. $\frac{3M}{4}$

Answer 1

Answer: (D)

$\frac{3M}{4}$

$H_3\stackrel{+1}{P}{O}_2\to H_3\stackrel{+3}{P}{O}_3;Eq.wt.=\frac{M}{2}$
(Change in oxidation number $=2$)
$H_3\stackrel{+1}{P}{O}_2\to P\stackrel{-3}{H_3};Eq.wt.=\frac{M}{4}$
(Change in oxidation number $=4$)
The equivalent mass of $H_{3}P{O}_2$ in the process of disproportionation $=\frac{M}{2}+\frac{M}{4}=\frac{3M}{4}$.