An ideal monatomic gas is taken round the cycle ABCD as shown in the Fig. The work done during the cycle is

 

 

The work done during the cyclic path is equal to the area
enclosed by the path, which is pV.

Work done

$\begin{array}{l}=(2\mathrm{p}-\mathrm{p})(2\mathrm{V}-\mathrm{V})\\ =\mathrm{pV}\end{array}$