# During which of the following processes,

Question:

During which of the following processes, does entropy decrease?

(A) Freezing of water to ice at $0^{\circ} \mathrm{C}$

(B) Freezing of water to ice at $-10^{\circ} \mathrm{C}$

(C) $\mathrm{N}_{2}(\mathrm{~g})+3 \mathrm{H}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{NH}_{3}(\mathrm{~g})$

(D) Adsorption of $\mathrm{CO}(\mathrm{g})$ and lead surface

(E) Dissolution of $\mathrm{NaCl}$ in water

1. (A), (B), (C) and (D) only

2. (B) and (C) only

3. (A) and (E) only

4. (A), (C) and (E) only

Correct Option: 1

Solution:

(A) Water $\stackrel{0^{\circ} \mathrm{C}}{\longrightarrow}$ ice; $\Delta \mathrm{S}=-$ ve

(B) Water $\stackrel{-10^{\circ} \mathrm{C}}{\longrightarrow}$ ice; $\Delta \mathrm{S}=-$ ve

(C) $\mathrm{N}_{2}(\mathrm{~g})+3 \mathrm{H}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{NH}_{3}(\mathrm{~g}) ; \Delta \mathrm{S}=-\mathrm{ve}$

(D) Adsorption; $\Delta \mathrm{S}=-\mathrm{ve}$

(E) $\mathrm{NaCl}(\mathrm{s}) \rightarrow \mathrm{Na}^{+}(\mathrm{aq})+\mathrm{Cl}^{-}(\mathrm{aq}) ; \Delta \mathrm{S}=+\mathrm{ve}$