Question

Phosphine $P{H}_3$ cannot be formed by which of the following reactions

• A. Reaction of phosphonium iodide with potassium hydroxide
• B. By hydrolysis of Calcium phosphide
• C. By heating phosphoric acid
• D. By heating white phosphorus with concentrated sodium hydroxide

Answer 1

The correct option is C By heating phosphoric acid

Calcium phosphide on hydrolysis or reaction with dil. HCl gives cacium hydroxide and phosphine
$C{a}_3{P}_2+H_{2}O\to 3Ca(OH{)}_2+P{H}_3$
Reaction of phoshoniumiodide on treating with KOH gives
$P{H}_{4}I+KOH\to KI+H_{2}O+P{H}_3$
Phosphoric acid does not decompose to phosphine but phosphorus acid on heating gives:
$H_{3}P{O}_3\stackrel{Heat}{\to }{H}_{3}P{O}_4+P{H}_3$