Question

In which of the following \(\Delta E = \Delta H\)?

• A. \(N_2O_4(g) \rightleftharpoons 2NO_2(g)\)
• B. \(2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)\)
• C. \(H_2(g) + I_2(g) \rightleftharpoons 2HI(g)\)
• D. \(H_2(g) + \frac{1}{2}O_2(g) \rightleftharpoons H_2O(l)\)

Hint:

If gaseous moles are same on both sides → \(\Delta E = \Delta H\).

Answer 1

The Correct Option is C

Concept: \[ \Delta H = \Delta E + \Delta n_g RT \]

Step 1: Condition.
\(\Delta E = \Delta H\) when \(\Delta n_g = 0\)

Step 2: Check reactions.
(A) \(1 \to 2\) change in moles $\times$
(B) \(3 \to 2\) $\times$
(C) \(2 \to 2\) \checkmark
(D) gas to liquid $\times$

Step 3: Conclusion.
Correct option is (C)