Question

100 mL of PH₃ on heating forms P and H₂. The volume change in the reaction is:

• A. An increase of 50 mL
• B. An increase of 100 mL
• C. An increase of 150 ml
• D. A decrease of 50 mL

Answer 1

The correct option is A

An increase of 50 mL

$\underset{\mathrm{Phosphene}\mathrm{gas}}{4{\mathrm{PH}}_3\left(\mathrm{g}\right)}\to \underset{\mathrm{Phosphorous}}{4\mathrm{P}\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrogen}}{6{\mathrm{H}}_2\left(\mathrm{g}\right)}$

4-mole phosphene produces 6-mole hydrogen gas.

4 x 22400 ml phosphene produces 6 x 22400 ml hydrogen gas.

4 ml phosphene produces 6 ml hydrogen gas.

100 ml phosphene produces 150 ml hydrogen gas.

The volume change in the reaction is 150-100=50ml.

Hence, Option(A) is correct.