ok, so i encountered this problem on homework and i am really struggling with things like these. It's dealing with free energy. here's the question,

Determine the free energy change for the reaction: CuO(s) +H2(g) --> Cu(s) + H2O(l)

▲H (enthalpy: Hf-Hi) = -128.5 kJ/mol

▲S (entropy: Sf-Si) = -70.1 J/mol (would u change this to KJ/mol?)

I think in order to get this you need to use the formula ▲G (free energy)=▲H-T▲S. In the back of my book, it says that CuO = -128.3, H2 = 0, Cu = 0 and H2O = -237.1 (all in terms of ▲Gf). This is what i did so far,

Cu + H2O --> CuO + H2

(0 + - 237.1) - (-128.3 - 0) = -108.7 KJ/mol.

I think i got this totally wrong. can anyone help me and explain the right way to use what's listed and not listed for this problem? thanx a lot!

-Shinigami_Lover