100 mL of PH₃ when decomposed produces phosphorus and hydrogen. The change in volume is :

$$\begin{gathered} 4{\mathrm{PH}}_3\to {\mathrm{P}}_4+6{\mathrm{H}}_2 \\ 4\times 22400\mathrm{ml} 6\times 22400\mathrm{ml} \\ 100\mathrm{ml} ? \end{gathered}$$

${\mathrm{V}}_{{\mathrm{H}}_2}$liberated = $\frac{100}{4\times 22400}\times 6\times 22400=\frac{600}{4}=150\mathrm{ml}$