To determine the standard gibbs free energy, we need an equation that would relate chemical equilibrium and the free energy. We derive this expression from the relationship:
ΔG = ΔG° + RT ln Q
When the system is at equilibrium G = 0 which means the system had reached the minimum free energy. At this state, the reaction quotient is equal to the equilibrium constant. So, the reaction reduce to
0 = ΔG° + RT ln Kp
ΔG° = - RT ln Kp
We use this equation as follows: ΔG° = - RT ln Kp ΔG° = - 8.314 (1500 + 273.15) ln (1.4x10^-7) ΔG° = 232652.2047 J / mol
The standard Gibbs Free Energy at 1500 degrees Celsius is 232652.2047 J / mol.
