Question

Calculate the final centigrade temperature to change 20litres of gas at 120°c and 1atmosphere to 25litres at atmosphere.

Answer 1

The Gay-Lussac's law says

$$\frac{V_2}{V_1}=\frac{T_2}{T_1}$$

Hence, the final temperature

$$T_2=T_1\frac{V_2}{V_1}\\ =(120+273)*\frac{25}{20}=491\:\rm K=218\:{^\circ}C$$