Calculate heat released (in kJ) when 2 moles of gaseous methane undergoes combustion in a rigid vessel of volume 50 litres causing a change in pressure from 10 bar to 2 bar at 300 K.
[Useful data :
$\begin{array}{r}\mathrm{\Delta }{H}_f{\mathrm{H}}_2\mathrm{O}=-280\mathrm{kJ}/\mathrm{mole}\\ \mathrm{\Delta }{H}_f{\mathrm{CO}}_2=-390\mathrm{kJ}/\mathrm{mole}\\ \left.\mathrm{\Delta }{H}_f{\mathrm{CH}}_4=-70\mathrm{kJ}/\mathrm{mole}\right]\end{array}$