Question

Which statement is true? A reaction in which the entropy of the system decreases can be spontaneous only if it is exothermic. A reaction in which the entropy of the system increases can be spontaneous only if it is endothermic. A reaction in which the entropy of the system decreases can be spontaneous only if it is endothermic. A reaction in which the entropy of the system increases can be spontaneous only if it is exothermic.

Answer 1

Answer:

A reaction in which the entropy of the system decreases can be spontaneous only if it is exothermic.

Explanation:

The spontaneity of a reaction depends on the Gibbs free energy(ΔG).

• If ΔG < 0, the reaction is spontaneous.

• If ΔG > 0, the reaction is nonspontaneous.

ΔG is related to the enthalpy (ΔH) and the entropy (ΔS) through the following expression:

ΔG = ΔH - T.ΔS

where,

T is the absolute temperature (always positive)

Regarding the exchange of heat:

• If ΔH < 0, the reaction is exothermic.

• If ΔH > 0, the reaction is endothermic.

Which statement is true?

A reaction in which the entropy of the system decreases can be spontaneous only if it is exothermic. TRUE. If ΔS < 0, the term -T.ΔS > 0. ΔG can be negative only if ΔH is negative.

A reaction in which the entropy of the system increases can be spontaneous only if it is endothermic. FALSE. If ΔS > 0, the term -T.ΔS < 0. ΔG can be negative if ΔH is negative.

A reaction in which the entropy of the system decreases can be spontaneous only if it is endothermic. FALSE. If ΔS < 0, the term -T.ΔS > 0. ΔG cannot be negative if ΔH is positive.

A reaction in which the entropy of the system increases can be spontaneous only if it is exothermic. FALSE. If ΔS > 0, the term -T.ΔS < 0. ΔG can be negative even if ΔH is positive, as long as |T.ΔS| > |ΔH|.