Question 1

What is the difference between ΔG and ΔG°?

Accepted Answer

ΔG is the reaction Gibbs energy change under the current conditions, while ΔG° is the standard Gibbs energy change. Equilibrium requires ΔG = 0 for the actual reaction state; it does not generally require ΔG° to be zero.

Question 2

How does Gibbs energy predict spontaneity?

Accepted Answer

At constant temperature and pressure, ΔG < 0 indicates a spontaneous forward change, ΔG = 0 indicates equilibrium, and ΔG > 0 indicates a non-spontaneous forward change. Spontaneous does not mean fast; it only describes thermodynamic tendency.

Question 3

What does the equilibrium constant K tell us?

Accepted Answer

K describes the equilibrium ratio of products and reactants under specified conditions. Since ΔG° = -RT ln K, a very large K requires a substantially negative ΔG° at a fixed temperature; a ΔG° close to zero gives K close to 1.

Question 4

Is equilibrium static or dynamic?

Accepted Answer

Equilibrium is dynamic. Forward and reverse reactions continue at equal rates, so the macroscopic composition remains constant even though microscopic particles keep reacting.

Question 5

What is the second law of thermodynamics?

Accepted Answer

The second law states that the total entropy of the system plus surroundings never decreases for a spontaneous process. For an irreversible spontaneous process it increases, while at equilibrium or for an ideal reversible process the total entropy change can be zero.

Gibbs Energy & Entropy Lab — Will It Run?

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