Explanation

(b) At constant pressure,
Heat required$= nC_{p}\mathrm{\Delta}T$
$\Rightarrow \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 310 = 2 \times C_{p} \times (35 - 25)$
$\Rightarrow \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ C_{p} = \frac{310}{20} = 15.5J/mol/K$
Similarly, at constant volume,
Heat required$= nC_{V}\mathrm{\Delta}T$
$= 2\left( C_{p} - R \right) \times (35 - 25)\ \ \ \ \ \ \ \ \ \left( \because C_{p} - C_{v} = R \right)$
$= 2 \times (15.5 - 8.3) \times 10$
$= 2 \times 7.2 \times 10 = 144\ J$