1. The problem statement, all variables and given/known data Calculate the vapor pressure of water at 25°C, based on the Gibbs free energy when vaporising from liquid water to vapor (so at 1 atm and 25°C ). 2. Relevant equations 3. The attempt at a solution After integrating d g/d p= RT/p. I get my formula p = p0*exp (-delta gm(p0, T)/RT). I know all these variables, except for delta gm. So the gibbs free energy at 1 atm and 25°C. When differentiating G = H -TS: dG = (dG/dp)T*dp + (dG/dT)p*dT (partial derivative to p, when T is constant multiplied by change in pressure + partial derivative to T when p is constant multiplied by change in temperature) Since there is no change in temperature only the partial derivative to p when T is constant is of importance. Which is equal to volume. I know the value should be 8560 J/mol, but no method I have used seems to give me the right answer. I posted this on my phone. Sorry for not using proper symbols.