Question

Calculate the change in volume of gases when $1$ mole of $P{H}_3$ decomposed at STP according to given reaction:
$P{H}_3\left(g\right)\to \frac{1}{4}{P}_4\left(g\right)+\frac{3}{2}{H}_2\left(g\right)$

• A. $22.7$
• B. $\frac{7}{4}\times 22.7$
• C. $\frac{3}{4}\times 22.7$
• D. $\frac{7}{2}\times 22.7$

Answer 1

The correct option is C $\frac{3}{4}\times 22.7$

When 1 mole of $P{H}_3$ decomposes at STP, the change in the number of moles of gaseous species is
$\Delta n=\frac{1}{4}+\frac{3}{2}-1=\frac{3}{4}$
When we multiply $\Delta n$ with 22.4, we get the change in volume of gases.
The change in volume of gases $=\frac{3}{4}\times 22.4$ L.