devarshi-dt-logo

Question:

The process with negative entropy change is:
dissolution of iodine in water.
dissociation of CaSO4(s) to CaO(s) and SO3(g)
synthesis of ammonia from N2 and H2
sublimation of dry ice

dissociation ofCaSO4(s)toCaO(s)andSO3(g)

dissolution of iodine in water.

synthesis of ammonia fromN2andH2

sublimation of dry ice

Solution:

In option A, solid dissolves to form an aqueous solution and hence entropy increases. In option B, four moles of gas (N2 + 3H2 → 2NH3) 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.