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How does partial pressure affect Gibbs free energy?

Answer 1

Avery Adams

#DeltaG=DeltaG^@+RTln(((P_(NH_3))^2)/((P_(N_2))(P_(H_2))^3))#

Consider the following reaction:

#N_2(g) +3H_2(g) rightleftharpoons 2NH_3(g)#

The free energy of this equilibrium could be found by the following expression:

#DeltaG=DeltaG^@+RTlnK#

where #K# is the equilibrium constant that is given by:

#K=((P_(NH_3))^2)/((P_(N_2))(P_(H_2))^3)#

Therefore, the Gibbs free energy is related to the partial pressure by:

#DeltaG=DeltaG^@+RTln(((P_(NH_3))^2)/((P_(N_2))(P_(H_2))^3))#

Here is a video that explains the origin on this expression in details:

Thermodynamics | Free Energy, Pressure & Equilibrium.

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Answer 2

Peyton Adams

Partial pressure affects Gibbs free energy through its influence on the chemical potential of a substance in a mixture. The relationship is described by the Gibbs-Duhem equation, which states that the change in Gibbs free energy with respect to changes in pressure is equal to the molar volume of the substance multiplied by the change in pressure. Specifically, an increase in partial pressure increases the chemical potential of a substance, leading to a decrease in its Gibbs free energy, and vice versa.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.