Question

Which of the following relations is correct for a reaction \(\text{S}_{(s)}+\text{O}_{2(g)}\rightarrow \text{SO}_{2(g)}\) ?

• A. \(\Delta H > \Delta U\)
• B. \(\Delta H < \Delta U\)
• C. \(\Delta H = 0\)
• D. \(\Delta H = \Delta U\)

Hint:

Count gaseous moles: one mole of gas on each side, so delta n g is zero.

Answer 1

The Correct Option is D

Step 1: Work done by gases:
The gap between $\Delta H$ and $\Delta U$ is the pressure-volume work $P\Delta V$. For ideal gases it equals $\Delta n_g RT$.

Step 2: Count gas moles:
Solid sulfur does not count. Left side has 1 mol of gas, right side has 1 mol of gas, so there is no volume change at constant pressure.

Step 3: Conclusion:
$P\Delta V = 0$, hence $\Delta H = \Delta U$. This is option (D).

Final Answer:
Because delta n g = 0, delta H = delta U. \[ \boxed{\text{(D) }\Delta H=\Delta U} \]