What is the significance of Gibbs free energy?

Gibbs Energy question?

• Here's the problem: A chemical reaction at 1.0 bar and 298 K has ΔrG° = -335 kJ/mol. The Gibbs function of the reactants changes by +7.5 kJ/mol when the pressure is changed from 1.0 bar to some other pressure P2. The products change by +8.4 kJ/mol over the same pressure change, 1.0 bar to P2. What is ΔrG° at P2 and 298 K? Relevant equations (Maybe?): ΔG = ΔG° + RTln(P2/P1) I'm not sure what to do with the Gibbs functions of the reactants and products. Can I subtract reactants from products (8.4 - 7.5) to get ΔrG? I did this and plugged all of the numbers into the above formula, solving for P2 = 7.52 bar. What now? Am I on the right track at all?

• Answer:

  I'm guessing the Gibbs function is what I would call 'ΔG', not 'ΔrG'. I'm very rusty on this stuff, but I suspect the problem is actually basic/simple. Going from 1bar to P2 (temperature constant at 298K): The Gibbs function of the reactants changes by +7.5 kJ/mol The Gibbs function of the products changes by +8.4 kJ/mol Overall the Gibb's function changes by 8.4 - 7.5 = 0.9 kJ/mol ΔG° at P2 = -335 + 0.9 = -334.1 kJ/mol (= -334 kJ/mol to 3 significant figures) I'm not 100% sure - it might be worth asking in Chemistry, as this is more of a Chemistry than Physics question.