$\mathrm{P}_{2} \mathrm{H}_{4}$ can be removed from phosphine containing traces of it

$\mathrm{P}_{2} \mathrm{H}_{4}$ can be removed from phosphine containing traces of it
  1. by passing impure $\mathrm{PH}_{3}$ gas through a freezing mixture.
  2. by passing the impure $\mathrm{PH}_{3}$ gas through HI and then its treatment with $\mathrm{KOH}$ (aq).
  3. by both (a) and (b).
  4. by none of these.

Solution

Both the methods (a) and (b) can be used. When passed through freezing mixture the $\mathrm{P}_{2} \mathrm{H}_{4}$ present condenses and pure $\mathrm{PH}_{3}$ is obtained.
When passed through HI, $\mathrm{PH}_{3}$ is absorbed forming $\mathrm{PH}_{4} \mathrm{I} . \mathrm{PH}_{4} \mathrm{I}$ when treated with $\mathrm{KOH}$
(aq) yields pure phosphine.
$\mathrm{PH}_{3}+\mathrm{HI} \longrightarrow \mathrm{PH}_{4} \mathrm{I}$
$\mathrm{PH}_{4} \mathrm{I}+\mathrm{KOH}(\mathrm{aq}) \longrightarrow \mathrm{KI}+\mathrm{H}_{2} \mathrm{O}+\mathrm{PH}_{3} \uparrow$

Asked in: JEE-TOPICTESTS-CHEMISTRY

Practice more P-BLOCK ELEMENTS GROUP 15 16 17 18 questions on Aicharya