Question

White phosphorus can be separated from red phosphorus by:

• A. Sublimation
• B. Distillation
• C. Dissolving in $C{S}_2$
• D. Heating with alkali solution

Answer 1

Answer: (C), (D)

Heating with alkali solution

Red phosphorus doesn't easily react with $NaOH$. This is in contrast with white phosphorus:

$P_4+3NaOH+3H_{2}O⟶P{H}_3\uparrow +3Na{H}_{2}P{O}_2$

Don't forget that the general rule for sulibility is "like dissolves like."

White phosphorus is a molecular solid made of non-polar $P_4$ units. Hence, it is soluble in non-polar solvents like $C{S}_2$, while red phosphorus is not!