(i)Entropy of vapourisation – (b)is always positive

Explanation: When the liquid vaporizes, the degree of the disorder increases, therefore, entropy is always positive.

(ii) K for the spontaneous process- (d) the ideal gas

Explanation: K is equilibrium constant and is always positive.∆_rH^- is large and positive for strong endothermic reaction and the value of K is smaller than 1.

∆_rH^- is large and negative for exothermic reaction and the value of K is larger than 1. ∆_rG^- is also negative and large.

To get a large value of K we need a strongly exothermic reaction, hence we go for completion of the reaction.

∆_rG^- depend on ∆_rS^- and if entropy changes then the value of K also get affected, which depend on whether ∆_rS^- is positive or negative.

(iii) Crystalline solid-state : (c) lowest entropy

Explanation: Crystalline solid state is the most ordered form so it has the lowest entropy and gaseous state is disordered state so highest entropy.

(iv) ΔU in adiabatic expansion – (a) decreases

Explanation, as there is no exchange of heat between system and surrounding, internal energy will decrease after applying some amount of pressure.