What volume of oxygen gas $\left(\mathrm{O}_2\right)$ measured at $0^{\circ} \mathrm{C}$ and 1 atm, is…
What volume of oxygen gas $\left(\mathrm{O}_2\right)$ measured at $0^{\circ} \mathrm{C}$ and 1 atm, is needed to burn completely $1 \mathrm{~L}$ of propane gas $\left(\mathrm{C}_3 \mathrm{H}_8\right)$ measured under the same conditions?
$10 \mathrm{~L}$
$7 \mathrm{~L}$
$6 \mathrm{~L}$
$5 \mathrm{~L}$
Solution
$\begin{aligned}
& \underset{22.4 \mathrm{~L} \text { at STP }}{\mathrm{C}_3 \mathrm{H}_8(\mathrm{~g})}+\underset{5 \times 22.4 \mathrm{~L} \text { at STP }}{5 \mathrm{O}_2(\mathrm{~g})} \rightarrow 3 \mathrm{CO}_2(\mathrm{~g})+4 \mathrm{H}_2 \mathrm{O}(\mathrm{I}) \\
& \because 22.4 \mathrm{~L} \mathrm{C}_3 \mathrm{H}_8 \text { at STP } \equiv 5 \times 22.4 \mathrm{~L} \text { of } \mathrm{O}_2 \text { at STP } \\
& \therefore 1 \mathrm{LC}_3 \mathrm{H}_8 \text { at STP } \equiv \frac{5 \times 22.4}{22.4} \text { of } \mathrm{O}_2 \text { at STP } \\
& =5 \mathrm{~L} \text { of } \mathrm{O}_2 \text { at NTP } \\
&
\end{aligned}$