A sample of nitrogen occupies a volume of $320c{m}^3$  at STP. Calculate its volume at 546.3K and 0.5bar pressure. 

Given, 
$\begin{array}{l}{P}_1=1.0bar,P_2=0.5bar\\ V_1=320c{m}^3,V_2=?\\ T_1=273.15K,T_2=546.3K\end{array}$
According to gas equation, we get 
 $\begin{array}{l}\frac{P_1{V}_1}{T_1}=\frac{P_2{V}_2}{T_2}\\ \therefore V_2=\frac{P_1{V}_1\times T_2}{T_1\times P_2}=\frac{1\times 320\times 546.3}{273.15\times 0.5}=1280c{m}^3\end{array}$