Question

Assertion : Decrease in free energy causes spontaneous reaction.

Reason : Spontaneous reactions are invariably exothermic reactions

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not correct explanation of A

(c) A is true but R is false

(d) A and R are false

Answer 1

Correct option  (b) Both A and R are true but R is not correct explanation of A

Explanation:

Gibbs free energy (ΔG) is given by :

ΔG = ΔH-TΔS

ln chemical systems, the reaction moves in a direction in which there is decrease in free energy i.e.,

ΔG = -ve.

Also, decrease in free energy is a measure of the maximum useful work that can be obtained from a reaction. But the reaction can be exothermic or endothermic e.g., water evaporation is endothermic but it is a spontaneous process (i.e., ΔG = -ve.)