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: Understanding the Concept:
\(\Delta H\) and \(\Delta U\) differ by the work term due to change in the number of moles of gas.

Step 2: Key Formula or Approach:
\[ \Delta H = \Delta U + \Delta n_g RT \]

Step 3: Detailed Explanation:
In \(\text{S}_{(s)} + \text{O}_{2(g)} \rightarrow \text{SO}_{2(g)}\), only gases are counted: reactant gas = 1 mol of \(\text{O}_2\), product gas = 1 mol of \(\text{SO}_2\).
So \(\Delta n_g = 1 - 1 = 0\).
Then \(\Delta H = \Delta U\).
Options (A) and (B) need a nonzero \(\Delta n_g\). Option (C) says \(\Delta H = 0\), which has no basis because combustion releases heat.

Step 4: Final Answer:
\(\Delta H = \Delta U\), option (D).

Final Answer:
Delta n g is zero, so delta H equals delta U. \[ \boxed{\text{(D) }\Delta H=\Delta U} \]