FREE ENERGY AND THE EQUILIBRIUM CONSTANT

Pink Floyd’s “Wish You Were Here” Cover

Storm Thorgerson, 1975

ΔG^o and the Equilibrium Constant, K

Qualitative Analysis of This Relationship

Qualitative Analysis of This Relationship

Qualitative Analysis of This Relationship

Summary of Relationship Between K and ΔG^O

If K > 1then ΔG^o < 0 (negative), so process is thermodynamically favorable.

If K < 1then ΔG^o > 0 (positive), so process is not thermodynamically favorable.

If K = 1then ΔG^o = 0, so process is at equilibrium.

Practice Problem

Use tabulated free energies of formation to calculate the equilibrium constant for the reaction at 298 K:

N₂O₄(g) ⇌ 2 NO₂(g)

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2.80x10³ J/mol = -(8.3145 J/molK)(298 K)(ln K)

-1.1301 = ln K

K = 0.323

= 2.80 kJ

Concept Check

Concept Check

Concept Check