Question:
At constant volume, $4 \mathrm{~mol}$ of an ideal gas when heated from $300 \mathrm{~K}$ to $500 \mathrm{~K}$ changes its internal energy by $5000 \mathrm{~J}$. The molar heat capacity at constant volume is __________________ .
Solution:
$(6.25) \quad \Delta U=n C_{v} \Delta T$
$5000=4 \times C_{v}(500-300)$
$\mathrm{C}_{\mathrm{v}}=6.25 \mathrm{JK}^{-1} \mathrm{~mol}^{-1}$