Question

The temperature of $5$ moles of a gas at constant volume is changed from $100{}^{\circ }C$ to $120{}^{\circ }C$ . The change in internal energy is $80J$ . The total heat capacity of the gas at constant volume (in $J{K}^{-1}$ ) is

• A. $8$
• B. $4$
• C. $0.8$
• D. $0.4$

Answer 1

Answer: (B)

Number of moles $n=5mol,T_1=100^{\circ }C$
$T_2=120^{\circ }C,\Delta U=80J$
Rise in temperature $\Delta T=120-100=20^{\circ }C$
$\Delta U=ms\Delta T$
$\frac{80}{5}=1\times s\times 20$
$s=\text{0.8}J$
$\therefore$ For $5$ mol, $s=\text{0.8}\times 5J{K}^{-1}=4J{K}^{-1}$