Question

A diatomic gas, with rigid molecules, does $10\text{J}$ of work when expanded at constant pressure. What would be the heat energy absorbed by the gas, in this process ?

• A. $30\text{J}$
• B. $40\text{J}$
• C. $25\text{J}$
• D. $35\text{J}$

Answer 1

The correct option is D $35\text{J}$

For an isobaric process, $W=P\Delta V=nR\Delta T=10\text{J}$

For a rigid diatomic gas,
$C_p=\frac{7}{2}R$
Now, $Q=n{C}_p\Delta T=n\frac{7}{2}R\Delta T$

$\therefore Q=\frac{7}{2}\left(nR\Delta T\right)=\frac{7}{2}\times 10=35\text{J}$

Hence, $\left(B\right)$ is the correct answer.