$\begin{aligned}
& \mathrm{dQ}=\mathrm{du}+\mathrm{dW} \
& \mathrm{CdT}=\mathrm{C}_{\mathrm{V}} \mathrm{dT}+\mathrm{PdV} \
& \therefore \mathrm{PV}^2=\mathrm{RT} \
& \mathrm{P}=\text { constant } \
& \mathrm{P}(2 \mathrm{VdV})=\mathrm{RdT} \
& \mathrm{PdV}=\frac{\mathrm{RdT}}{2 \mathrm{~V}} \
&
\end{aligned}$
Put in equation (1) C=CV+2 VR