Question

The process with negative entropy change is:

• A. dissolution of iodine in water.
• B. synthesis of ammonia from $N_2$ and $H_2$
• C. dissociation of $CaS{O}_4\left(s\right)$ to $CaO\left(s\right)$ and $S{O}_3\left(g\right)$
• D. sublimation of dry ice

Answer 1

Answer: (B)

synthesis of ammonia from $N_2$ and $H_2$

• In option A, solid dissolves to form an aqueous solution and hence entropy increases.

• In option B, four moles of gas $(N_2+3H_3\to 2N{H}_3)$ reacts to give only two moles of gas and hence entropy decreases.

• In option C, a solid is converting into gas and thus entropy increases.

• In option D, the reaction is that a solid is converting into gas and thus entropy increases.

So, option B is the correct answer.