Half Reactions

Moderators: Chem_Mod, Chem_Admin

RyanTran2F
Posts: 44
Joined: Thu Jul 27, 2017 3:00 am

Half Reactions

Postby RyanTran2F » Wed Feb 07, 2018 1:33 pm

If a question asks for the half reactions, do we write it in the order it was given in the equation or always write it as a reduction process (similar to the reaction in the table)? Thanks :)

Clara Rehmann 1K
Posts: 53
Joined: Fri Sep 29, 2017 7:03 am

Re: Half Reactions

Postby Clara Rehmann 1K » Wed Feb 07, 2018 1:36 pm

I think either is okay, but to be thorough maybe label them as "reduction" and "oxidation" or "anode" and "cathode."

Eli Aminpour 2K
Posts: 50
Joined: Fri Sep 29, 2017 7:04 am

Re: Half Reactions

Postby Eli Aminpour 2K » Wed Feb 07, 2018 3:31 pm

don't write both half reactions as reductions. Make sure to write the complete oxidation and reduction reactions, and as the person above me said, labeling is good for that too.

Diane Bui 2J
Posts: 61
Joined: Sat Jul 22, 2017 3:00 am

Re: Half Reactions

Postby Diane Bui 2J » Wed Feb 07, 2018 3:57 pm

Just to add on, like Dr. Lavelle mentioned today in class, we should be careful with which method we are using and the signs of our standard reduction potentials.

Mitch Walters
Posts: 45
Joined: Fri Sep 29, 2017 7:07 am

Re: Half Reactions

Postby Mitch Walters » Wed Feb 07, 2018 11:57 pm

It shouldn't matter, because when you add them together you always end up with the original reaction.

Amanda Wu 2C
Posts: 31
Joined: Sat Jul 22, 2017 3:00 am

Re: Half Reactions

Postby Amanda Wu 2C » Thu Feb 08, 2018 1:30 pm

If you use the second method Lavelle spoke about in class to calculate the standard reduction potential of the cell, you first identify the half reactions and look up the standard reduction potentials of these respective half reactions. Thus, I believe, in the tables, you'll notice that the half reactions are written as reduction reactions because the values for the reduction potentials are given. However, when you proceed to balance the half reactions and write out the cell reaction, you'll eventually flip one of the reactions (the one that is supposed to be an oxidation) so it becomes an oxidation reaction and just negate the given standard reduction potential before summing the two equations together.

Jennifer Ho 1K
Posts: 31
Joined: Thu Jul 13, 2017 3:00 am

Re: Half Reactions

Postby Jennifer Ho 1K » Thu Feb 08, 2018 9:37 pm

All the half reactions are written as reductions for the sake of consistency; they could just as easily be all written as oxidation reactions (and I think some tables have it like that). When writing the half reactions you should write it with one reduction and one oxidation half reaction, and for the reaction you flip, you need to flip the sign of the potential.


Return to “Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams”

Who is online

Users browsing this forum: No registered users and 2 guests