What is the sign of ΔH (system)and ΔS (system)if a chemical reaction is spontaneous only at lower temperatures under standard conditions?
A) ΔH (system)is negative,and ΔS (system)is negative.
B) ΔH (system)is positive,and ΔS (system)is positive.
C) ΔH (system)is positive,and ΔS (system)is negative.
D) ΔH (system)is negative,and ΔS (system)is positive.
E) None of these

Question

Quizplus · Accepted Answer

For a reaction to be spontaneous at lower temperatures, ΔH must be negative (exothermic) and ΔS must be negative (decrease in entropy). This ensures that the negative ΔH term dominates the Gibbs free energy equation (ΔG = ΔH - TΔS) at lower temperatures, making ΔG negative and the reaction spontaneous.

What Is the Sign of ΔH (System)and ΔS (System)if a Chemical