Adding water  [ENDORSED]

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smurphy1D
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Joined: Mon Nov 18, 2019 12:18 am

Adding water

Postby smurphy1D » Sat Mar 14, 2020 5:19 pm

If pure water is added to either a cathode or anode, would it change the E at all?

romina_4C
Posts: 100
Joined: Thu Jul 11, 2019 12:17 am

Re: Adding water

Postby romina_4C » Sat Mar 14, 2020 5:21 pm

Adding pure water to the cathode or to the anode would decrease the concentration at the cathode/anode, thus increasing the cell potential because theres a bigger difference between the concentration of the anode/cathode (only if you only dilute one, not if you dilute both the same amount).

Anuradha S 1F
Posts: 50
Joined: Fri Sep 27, 2019 12:29 am

Re: Adding water

Postby Anuradha S 1F » Sat Mar 14, 2020 8:41 pm

I don't think that's correct. According to class notes, when concentration decreases (ie when pure water is added), cell potential will decrease. Not sure about the reasoning, so if anyone knows, please comment!

Adriana_4F
Posts: 74
Joined: Fri Sep 28, 2018 12:29 am

Re: Adding water

Postby Adriana_4F » Sat Mar 14, 2020 8:58 pm

This is a bit confusing, someone please clarify!

Chem_Mod
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Re: Adding water  [ENDORSED]

Postby Chem_Mod » Sat Mar 14, 2020 9:09 pm

romina_4C wrote:Adding pure water to the cathode or to the anode would decrease the concentration at the cathode/anode, thus increasing the cell potential because theres a bigger difference between the concentration of the anode/cathode (only if you only dilute one, not if you dilute both the same amount).


This answer is not completely correct. It's best not to make sweeping generalizations and instead think about it conceptually: Increasing the concentration gradient increases the cell potential. Let's take a simple case of a concentration cell.
1. If you dilute the solution at the cathode (higher concentration initially), you decrease its concentration. This makes the concentrations at the anode and cathode more similar. This decreases the concentration gradient and thus the cell potential.
2. If you dilute the solution at the anode (lower concentration initially), you decrease its concentration. This makes the concentrations at the anode and cathode more different. This increases the concentration gradient and thus the cell potential.


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