Question

Heat is supplied to a diatomic gas at constant pressure. The ratio of $\Delta Q:$$\Delta$U:$\Delta$W is:

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

Answer 1

The correct option is B 7:5:2

For a diatomic gas,

$C_V=\frac{5}{2}R$

$C_P=\frac{7}{2}R$

We know that

$\therefore \Delta Q=n{C}_P\Delta T=n\left(\frac{7}{2}R\right)\Delta T$

$\Delta U=n{C}_V\Delta T=n\left(\frac{5}{2}R\right)\Delta T$

According to first law of thermodynamics,

$\Delta W=\Delta Q-\Delta U=nR\Delta T$

$\therefore \Delta Q:\Delta U:\Delta W=7:5:2$