Given

• Diatomic gas with $\gamma = 1.4$
• Isobaric expansion
• Work done by gas: $W = 200\,\text{J}$

Use the relation for an isobaric process

For an ideal gas in an isobaric process, $W = nR\Delta T$

Heat supplied is $Q = nC_p\Delta T$

Therefore, $\frac{Q}{W} = \frac{C_p}{R}$

Find $C_p$ using $\gamma$

We know $\gamma = \frac{C_p}{C_v} = 1.4$ and $C_p - C_v = R$

Using the standard relation, $C_p = \frac{\gamma R}{\gamma - 1}$

So, $\frac{C_p}{R} = \frac{\gamma}{\gamma - 1} = \frac{1.4}{0.4} = 3.5$

Calculate heat supplied

$Q = W\cdot \frac{C_p}{R} = 200 \times 3.5 = 700\,\text{J}$

Match with the options

$Q = 700\,\text{J}$

So the correct option is C.

Comparison with stored answer

Stored correct answer: C

Our derived answer: C

Hence, they agree.