Question

Match the column $I$ with column $II$ and mark the appropriate choice.

Column I		Column II
(A)	$H_{2\left(g\right)}+Br_{2\left(g\right)} \to 2HBr_{\left(g\right)}$	(i)	$\Delta H = \Delta U - 2RT$
(B)	$PCl_{5\left(g\right)} \to PCl_{3\left(g\right)}+Cl_{2\left(g\right)}$	(ii)	$\Delta H = \Delta U + 3RT$
(C)	$N_{2\left(g\right)} \to 3H_{2\left(g\right)}+2NH_{3\left(g\right)}$	(iii)	$\Delta H = \Delta U$
(D)	$2N_{2}O_{5\left(g\right)} \to 4NO_{2\left(g\right)}+O_{2\left(g\right)}$	(iv)	$\Delta H = \Delta U + RT$

• A. $(A) \to (iii)$, $(B) \to (i)$, $(C) \to (ii)$, $(D) \to (iv)$
• B. $(A) \to (iii)$, $(B) \to (iv)$, $(C) \to (i)$, $(D) \to (ii)$
• C. $(A) \to (ii)$, $(B) \to (i)$, $(C) \to (iv)$, $(D) \to (iii)$
• D. $(A) \to (iv)$, $(B) \to (ii)$, $(C) \to (i)$, $(D) \to (iii)$

Answer 1

Answer: (B)

$(A) : \Delta n_g = 2-2 = 0$; hence $\Delta H = \Delta U$
$(B) : \Delta n_g = 2-1 = 1$; hence $\Delta H = \Delta U + RT$
$(C) : \Delta n_g = 2 - 4 = -2$; hence $\Delta H = \Delta U - 2RT$
$(D) : \Delta n_g = 5 - 2 = 3$; hence $\Delta H = \Delta U + 3RT$