Free Energy and Equilibrium Constant

The relationship between the standard free energy change and the equilibrium constant at a particular temperature is represented in an equation called the: Van’t Hoff Isotherm Equation

∆G^θ = -RT In K

From natural logarithms

In K = -2.303 log₁₀K

Therefore ∆G = -2.303 RT log₁₀K

Where:

G = standard Gibb’s free energy change

R = molar gas constant

T = temperature in Kelvin

K = Equilibrium constant

Example 8.5.1:

The free energy change for the reaction:

2Cu_[s] + 2NO_[g]  →  2CuO_[s] + N_2[g]  is -389 KJ at 25°C

What is the equilibrium constant for the reaction. ∆G = -2.303 RT logK

[R = 0.00831 atmdm³k^–mol^-1]

Solution: