- #1
Mr bboy
- 8
- 0
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 !
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 !