Hi everybody, I have some troubles to define the enthalpy and entropy of a half reaction. If we consider the 2 following reactions : Anode : H2 = 2H+ + 2e- Cathode : 2H+ + 2e- + 1/2O2 = H2O So the global reaction is : H2 + 1/2O2 = H2O We know the global reaction's entropy can be define as : ΔS H2O - ΔS H2 - 1/2*ΔS O2 We can do the same thing for the half reactions Anode : 2*ΔS H+ + 2*ΔS e- - ΔS H2 Cathode: ΔS H2O - 1/2*ΔS O2 - 2*ΔS H+ - 2*ΔS e- My problem is the following: how to define the entropy of hydrogen ion H+ and electron ? How can we define the entropy if half reaction ? I saw in many books people do the assumption to only consider the entropy at cathode side and so use the global reaction. Can u help me to solve this point ? Thank's !