What is the volume in $\mathrm{dm}^3$ occupied by $3 \mathrm{~mol}$ of ammonia gas at STP?
What is the volume in $\mathrm{dm}^3$ occupied by $3 \mathrm{~mol}$ of ammonia gas at STP?
$2.24$
$22.4$
$56.0$
$67.2$
Solution
$\begin{aligned} & \text { Number of moles of a gas }(\mathrm{n}) \\ & \quad=\frac{\text { Volume of a gas at STP }}{\text { Molar volume of a gas }} \\ & \therefore \quad \text { Volume of ammonia gas at STP } \\ & =\text { Number of moles of the gas }(\mathrm{n}) \\ & \quad \times \text { Molar volume of the gas } \\ & =3 \mathrm{~mol} \times 22.4 \mathrm{dm}^3 \mathrm{~mol}^{-1} \\ & =67.2 \mathrm{dm}^3\end{aligned}$