Predicting Spontaneity

Question 1

-H° and +S°

Answer 1

Spontaneous (ΔG < 0) for all temperatures

Question 2

+H° and -S°

Answer 2

Nonspontaneous (ΔG > 0) for all temperatures

Question 3

-H° and - S°

Answer 3

Spontaneous (ΔG < 0) at low temperatures but nonspontaneous (ΔG > 0) at high temperatures

Question 4

+H° and + S°

Answer 4

Spontaneous (ΔG < 0) at high temperatures but nonspontaneous (ΔG > 0) at low temperatures

Question 5

Reactions that are exothermic have a ________ H°

Answer 5

negative

Question 6

Reactions that are endothermic have a ________ H°

Answer 6

positive

Question 7

Reactions that increase in entropy have a ________ S°

Answer 7

positive

Question 8

Reactions that decrease in entropy have a ________ S°

Answer 8

negative

Question 9

When H° and S° have different signs, the spontaneity . .

Answer 9

does NOT depend on temperature

Question 10

When H° and S° have the same signs, the spontaneity . . .

Answer 10

DOES depend on temperature

Question 11

An exothermic reaction that increases in entropy will be . . .

Answer 11

Spontaneous (ΔG < 0) for all temperatures

Question 12

An endothermic reaction that decreases in entropy will be . . .

Answer 12

Nonspontaneous (ΔG > 0) for all temperatures

Question 13

An exothermic reaction that decreases in entropy will be . . .

Answer 13

Spontaneous (ΔG < 0) at low temperatures but nonspontaneous (ΔG > 0) at high temperatures

Question 14

An endothermic reaction that increases in entropy will be . . .

Answer 14

Spontaneous (ΔG < 0) at high temperatures but nonspontaneous (ΔG > 0) at low temperatures