## What half reaction to use 13.15b

AmirMahmoud_1J
Posts: 9
Joined: Fri Sep 26, 2014 2:02 pm

### What half reaction to use 13.15b

On 13.15 part B the question asks for the half reactons and a galvanic cell for H+(aq)+OH-(aq)-->H2O(l). There are two half recation pairs that give me the desired thermochemical reaction. (2H20+2e--->H2/2H2O+2e--->H2+2OH-) and (O2+4H+4e- --->2H2O/O2+2H2O+4e- --->4OH-). How do i tell which one to use?

AmirMahmoud_1J
Posts: 9
Joined: Fri Sep 26, 2014 2:02 pm

### Re: What half reaction to use 13.15b

in general how would one approach this problem.

Justin Le 2I
Posts: 142
Joined: Fri Sep 26, 2014 2:02 pm

### Re: What half reaction to use 13.15b

Did you make a typo when writing this out?
2H20+2e--->H2/2H2O+2e--->H2+2OH-

AmirMahmoud_1J
Posts: 9
Joined: Fri Sep 26, 2014 2:02 pm

### Re: What half reaction to use 13.15b

ya that should be 2H20+2e- -->H2+2OH- / 2H+ +2e- --> H2

Justin Le 2I
Posts: 142
Joined: Fri Sep 26, 2014 2:02 pm

### Re: What half reaction to use 13.15b

I think you can use either because they will both get you the same answer.