Question

Phosphine cannot be prepared by which of the following rreaction?

• A. White P is heated with NaOH
• B. Red P is heated with NaOH
• C. $C{a}_3{P}_2$ is heated with water
• D. Phosphorus trioxide is boiled with water

Answer 1

The correct option is B Red P is heated with NaOH

Red phosphorous does not reacts with caustic alkalies (NaOH or KOH). Whereas white phosphorus reacts with caustic alkalies to produce phosphine.
$\underset{whitephosphorus}{P_4}+3NaOH+3H_{2}O\to \underset{sodiumhypophosphite}{3Na{H}_{2}P{O}_2}+\underset{Phosphine}{P{H}_3}$
Phosphine is also obtained when calcium phosphide is heated with water.
$C{a}_3{P}_2+6H_{2}O\to 2P{H}_3+3Ca(OH{)}_2$
Phosphine is also obtained whn phosphorus trioxide is boiled with water.