Question

If heat energy $\Delta$ is supplied to an ideal diatomic gas and the increase in internal energy is $\Delta U$, the ratio of $\Delta U:\Delta Q$ is

• A. $7:5$
• B. $5:7$
• C. $5/2:7/2$
• D. $3:2$

Answer 1

Answer: (C)

$5/2:7/2$

For a diatomic gas, the specific heat at constant pressure $C_p=\frac{7}{2}R$ and the specific heat at constant volume $C_v=\frac{5}{2}R$

Thus, $\Delta U=n{C}_v\Delta T=\frac{5}{2}nR\Delta T$ and

$\Delta Q=n{C}_p\Delta T=\frac{7}{2}nR\Delta T$

Hence, $\Delta U:\Delta Q=5/2:7/2$