Thank you for reporting, we will resolve it shortly
Q.
The heat capacity per mole of water is ( $R$ is universal gas constant)
Kinetic Theory
Solution:
We treat water molecules like a solid. For each atom average energy is $3 k_{B} T$. Water molecule has three atoms, two hydrogen and one oxygen. The total energy of one mole of water is
$U=3 \times 3 k_{B} T \times N_{A}=9 R T $
$\left(\because k_{B}=\frac{R}{N_{A}}\right)$
$\therefore $ Heat capacity per mole of water is
$C=\frac{\Delta Q}{\Delta T}=\frac{\Delta U}{\Delta T}=9 R$