What is the sign of $\Delta$Hº(system)and $\Delta$Sº(system)if a chemical reaction is nonspontaneous at all temperatures under standard conditions?
A) ($\Delta$Hº)(system)is negative,and $\Delta$Sº(system)is positive.
B) ($\Delta$Hº)(system)is negative,and $\Delta$Sº(system)is negative.
C) ($\Delta$Hº)(system)is positive,and $\Delta$Sº(system)is positive.
D) ($\Delta$Hº)(system)is positive,and $\Delta$Sº(system)is negative.
E) none of these

Question

Quizplus · Accepted Answer

If a chemical reaction is nonspontaneous at all temperatures under standard conditions, then the Gibbs free energy change (∆Gº) must be positive. Since ∆Gº=∆Hº-T∆Sº, a positive ∆Gº implies that either ∆Hº is positive or ∆Sº is negative (or both). Therefore, (F1F1F1S1F1F1F10Hº)(system) must be positive (since ∆Hº must be positive) and F1F1F1S1F1F1F10Sº(system) must be negative (since ∆Sº must be negative). Therefore, the correct choice is D.

What Is the Sign Of Δ\DeltaΔ Hº(system)and Δ\DeltaΔ Sº(system)if a Chemical Reaction Is Nonspontaneous at All Temperatures Under

What Is the Sign Of $\Delta$ Hº(system)and $\Delta$ Sº(system)if a Chemical Reaction Is Nonspontaneous at All Temperatures Under