What happens to the value of K when ΔG becomes more positive?

Prepare for the ACS Physical Chemistry Thermochemistry Exam. Experience in-depth explanations and challenging multiple-choice questions to help you succeed in your exam.

The value of the equilibrium constant, K, is related to the change in Gibbs free energy, ΔG, through the equation:

[

ΔG = ΔG^\circ + RT \ln Q

]

At equilibrium, ΔG equals zero, and this leads to the relationship:

[

0 = ΔG^\circ + RT \ln K

]

From this equation, we can derive that:

[

ΔG^\circ = -RT \ln K

]

This indicates that if ΔG becomes more positive, ΔG^\circ must also become more positive. A more positive ΔG^\circ indicates that the reaction is less favorable in the forward direction. Since ΔG^\circ is inversely related to K through the equation, a more positive ΔG^\circ will result in a smaller value of K. This means the equilibrium position favors the reactants over the products, reflecting a decrease in K.

Thus, as ΔG becomes more positive, the value of K indeed gets smaller, confirming the validity of the answer.

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