We can, however, couple this rxn with one that does proceed spontaneously and force this rxn to proceed in the direction we want it to. The Thermodynamic Equilibrium Constant Thermodynamic Keq's are written exactly the same as we did previously, but concentrations of gases are expressed as partial pressures in atm's and concentrations of solutes in solution are expressed in molarities. As long as we don't have both gases and liquids in the equilibrium, our Keq's are exactly the same as previously. This tells us that the rxn will proceed spontaneously in the direction written. It is possible to precisely calculate the effect of temperature change on G, however these calculations are very complex.
G varies significantly with temperature.
This will give us the free energy change for the reaction at some specified temperature with the concentrations of the reactants at their standard states.