Assertion : For every chemical reaction at equilibrium, standard Gibbs energy of the reaction is zero.
Reason : At constant temperature and pressure, chemical reactions are spontaneous in the direction of the decreasing Gibbs energy.

Options

A. and (R) are correct and (R) is the correct explanation of(A).
B. If both (A) and (R) are correct, but (R) is not the correct explanation of(A).
C. If(A) is incorrect, but (R) is correct.
D. If both (A) and (R) are incorrect.

Answer

D

Explanation

For every chemical reaction at equilibrium, standard Gibbs energy of the reaction is not zero. It is zero only for the reactions at equilibrium. At constant temperature and pressure, the chemical reactions are spontaneous in the direction of decreasing Gibbs energy. For a reaction to be spontaneous, the free energy change should be negative or the free energy should decrease.