Question

White phosphorus can be separated from red phosphorus by________.

• A. sublimation
• B. dissolving in $C{S}_2$
• C. distillation
• D. heating with alkali solution

Answer 1

Answer: (B), (D)

White phosphorus is soluble in organic solvents such as $C{S}_2$, $CC{l}_4$.
Red phosphorus is insoluble in such solvents. Hence, white phosphorus can be separated from red phosphorus by dissolving in $C{S}_2$ or $anCC{l}_4$.
White phosphorus reacts with caustic alkalies ($NaOH$ and $KOH$).
Red phosphorus does not react with caustic alkalies ($NaOH$ and $KOH$).
Hence, white phosphorus can be separated from red phosphorus by heating with an alkali solution.

White phosphorous is boiled with aqueous $NaOH$ solution to obtain phosphine.
$P_4+3NaOH+3H_{2}O\to 3Na{H}_{2}P{O}_2+P{H}_3$