Gibbs free energy

Question 1

Equation for gibbs free energy

Answer 1

change in G = change in H(enthalpy) - T(in kelvins) x change in entropy
mnemonic: Get Higher Test Scores

Question 2

Will an endothermic reaction be spontaneous if the change in entropy is positive?

Answer 2

Only at high temperatures

G = (+H) - T x (+S) -> positive - higher positive = negative G

Question 3

Will an endothermic reaction be spontaneous if the change in entropy is negative?

Answer 3

No, it is non-spontaneous at all temperatures.

G = (+H) - T x (-S) -> positive - negative = positive + positive = positive G

Question 4

Will an exothermic reaction be spontaneous if the change in entropy is positive?

Answer 4

Yes, at all temperatures.

G = (-H) - T(+S) -> negative - positive = negative G

Question 5

Will an exothermic reaction be spontaneous if the change in entropy is negative?

Answer 5

Only at low temperatures.

G = (-H) - T(-S) = negative - lower negative = negative G, negative - higher negative = positive G

Question 6

Equation fr the overall free energy change in a reaction at STP?

Answer 6

G(reaction) = G(products) - G(reactants)

standard T = 298 K

Question 7

In a graph of free energy, where is change in G zero?

Answer 7

At the lowest point, where Qc(ratio of reactants to products) = Keq

Question 8

Equation relating G and Keq

Answer 8

G = -RTlnKeq

As Keq increases, amount of product increases, and G becomes more negative and spontaneous.

Question 9

If Keq is >1, which side of the reaction is favored, and why?

Answer 9

favors products - b/c ln(Keq) > 0 (+) and

G = -nRTlnKeq (-)(+) = (-)

Question 10

If Keq is

Answer 10

favors reactants - b/c ln(Keq)