Question

Phosphine $\left(P{H}_3\right)$ decomposes to produce vapours of phosphorus and $H_2$ gas. What will be the change in volume when 100 mL of phosphine is decomposed ?

• A. + 50 mL
• B. 500 mL
• C. + 75 mL
• D. - 500 mL

Answer 1

Answer: (C)

+ 75 mL

$4P{H}_3\left(g\right)\to P_4\left(g\right)+6H_2\left(g\right)$
$4mL\to 1mL6mL$
$100mL\to \frac{100}{4}\frac{6}{4}\times 100$
$100mL\to 25mL150mL$
Volume increases by 75 mL. ]