Anode and cathode in concentration cell?

Moderators: Chem_Mod, Chem_Admin

Kayla Denton 1A
Posts: 106
Joined: Fri Sep 26, 2014 2:02 pm

Anode and cathode in concentration cell?

Postby Kayla Denton 1A » Fri Feb 06, 2015 8:23 pm

In a concentration cell, for a reaction to be spontaneous, I understand that [products] must be less than [reactants]. I was wondering how this translated into anode and cathode; does the anode always contain the reactants and the cathode contains the products? So should the concentration in the cathode be less than the concentration of the anode?

The textbook gives an example of Ag+ (p. 540) and then says, "If the concentration of Ag+ ions in the left-hand electrode is less than that in the right, then Ecell > 0 for the cell as specified and the right-hand electrode will be found to be the cathode." This seems counterintuitive...

Any help would be much appreciated!

Chem_Mod
Posts: 17810
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 405 times

Re: Anode and cathode in concentration cell?

Postby Chem_Mod » Sat Feb 07, 2015 8:27 am

Look at the example I covered in class:

Anode: Ag was oxidized to Ag+ + 1e-. (The anode [Ag+] increases and is the 'product'.)

Cathode: Ag+ was reduced to Ag. (The cathode [Ag+] decreases and is the 'reactant'.)

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

Re: Anode and cathode in concentration cell?

Postby Justin Le 2I » Tue Feb 10, 2015 12:33 am

It's also useful to think of it as Q = [P]/[R]. If you have more products, then Q>1 and then the reaction favors the products. It's better just to use the ratio and think about it intuitively then to memorize the different cases.


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

Who is online

Users browsing this forum: No registered users and 1 guest