Positive or Negative Sign

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Karina Kong 2H
Posts: 98
Joined: Thu Jul 25, 2019 12:16 am

Positive or Negative Sign

Postby Karina Kong 2H » Sun Feb 23, 2020 9:46 pm

When do you change the sign of the value of the anode or cathode?

lilymayek_1E
Posts: 107
Joined: Sat Aug 17, 2019 12:16 am

Re: Positive or Negative Sign

Postby lilymayek_1E » Sun Feb 23, 2020 9:57 pm

you change the sign only on the anode because the anode is losing electrons (is the oxidation 1/2 reaction). every cell potential is given in reduction form, so you'll need to switch the sign to account for the oxidation 1/2 reaction.

Jonathan Gong 2H
Posts: 105
Joined: Sat Jul 20, 2019 12:16 am

Re: Positive or Negative Sign

Postby Jonathan Gong 2H » Sun Feb 23, 2020 9:59 pm

You change the sign of the reduction potential of the anode/cathode half-reactions based off of the direction of the half-reaction. For example, for Cu2+ + 2e- -> Cu, the standard reduction potential is 0.34 V. But, if this reaction occurs at the anode, then the half-reaction will actually be CU -> Cu2+ + 2e- with a standard reduction potential of -0.34 V. So, you would switch the sign of the reduction potential depending on whether the forward or reverse of the reaction is used.

205154661_Dis2J
Posts: 109
Joined: Wed Sep 18, 2019 12:21 am

Re: Positive or Negative Sign

Postby 205154661_Dis2J » Sun Feb 23, 2020 11:29 pm

As stated above, you would change the sign to positive or negative depending on the direction of the reaction from the standard reduction potential. That is why it is also very important to know whether a half reaction is an oxidation or reduction.

Shrayes Raman
Posts: 129
Joined: Sat Jul 20, 2019 12:15 am

Re: Positive or Negative Sign

Postby Shrayes Raman » Sun Feb 23, 2020 11:42 pm

The cell potential is given in reduction form so switch if oxidization is occuring.


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