Hello, I have some questions regarding the nernst equation at open circuit voltage. We know E(OCV) = E0+ ln (PH2*PO2^0.5 / PH2O) I have some trouble with this: If I have dry gas (both for O2 and H2), and my circuit is open at 25°C and 1 atm I have no water in the circuit so what become the nerst equation ? We have to neglect H2O? E(OCV) = E0+ ln (PH2*PO2^0.5 ) I am wondering why at OCV we take into account water since we don't create water because the circuit is open, and the only way that we could have water is from the reactants? Thank you for yout help !