Question

Assertion: Decrease in free energy causes spontaneous reaction.
Reason: Spontaneous reactions are invariably exothermic reactions.

• A. If both Assertion and Reason are true and the Reason is a correct explanation of the Assertion
• B. If both Assertion and Reason are true but Reason is not a correct explanation of the Assertion
• C. If Assertion is true but the Reason is false
• D. If both Assertion and Reason are false

Answer 1

Answer: (B)

Gibbs free energy ($\Delta$G) is given by :

$\Delta$G=$\Delta$H-T$\Delta$S

In chemical systems, the reaction moves in a direction in which there is decrease in free energy i.e. DG = -ve. Also, decrease in free energy is a measure of the maximum useful work that can be obtained from a reaction. But the reacton can be exotheremic or endothermic e.g. water evaporation is endothermic but it is a spontaneous process (i.e. $\Delta$G = -ve)