\Delta E_{\mathrm{int}} = Q = n C_V \Delta T. \Delta T = \dfrac{Q}{n C_V} 입니다.

\displaystyle

\Delta T = \dfrac{450\ \mathrm{J}} {(2.00\ \mathrm{mol}) \times \dfrac{3}{2} (8.314\ \mathrm{J/mol \cdot K})} \approx 18.04\ \mathrm{K}

\displaystyle

T_f = T_i + \Delta T \approx 318.0\ \mathrm{K}