Question

A diatomic gas is heated at constant pressure. lf 105 J of heat is given to the gas, find the change in internal energy of the gas.

Answer 1

Suppose the volume changes from $V_1$ to $V_2$ and the temperature changes from $T_1$ to $T_2$.

The heat supplied at
$\Delta Q=\Delta U+P\Delta V=\Delta U+nR\Delta T=\Delta U+\frac{2\Delta U}{f}[\Delta U=\frac{nfR\Delta T}{2}]$

The change in internal energy is
$\Delta Q=\Delta U[1+\frac{2}{f}]$

$105=\Delta U[1+\frac{2}{5}]\Rightarrow \Delta U=75J$