Positive vs Negative E value

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ChathuriGunasekera1D
Posts: 78
Joined: Fri Sep 28, 2018 12:17 am

Positive vs Negative E value

Postby ChathuriGunasekera1D » Mon Feb 18, 2019 7:37 pm

Hi! I had a quick question about determining how you know if the Ecell is positive or negative. I know that it's positive if the cathode is right and negative if the cathode is on the left, but the electron flow always goes towards the cathode regardless of what side the cathode is on. I'm wondering what difference a positive or negative sign makes on the value of Ecell. Thank you!

Toru Fiberesima 1L
Posts: 63
Joined: Fri Apr 06, 2018 11:02 am

Re: Positive vs Negative E value

Postby Toru Fiberesima 1L » Mon Feb 18, 2019 8:13 pm

The Ecell value is obtained from the two half reactions or the balanced chemical equation. Ecell is E(cathode) minus E(anode). For deltaG to be negative, which indicates that the reaction is a spontaneous one, E cell must be positive.

Angel Chen 2k
Posts: 59
Joined: Fri Sep 28, 2018 12:20 am

Re: Positive vs Negative E value

Postby Angel Chen 2k » Wed Feb 20, 2019 12:37 am

You determine the Ecell value from the two half-reactions you write from either the cell diagram given or the balanced chemical equation. The formula for calculating the Ecell is E(cathode) - E(anode) ( these values can be obtained from the book standard E value chart ). For example, electrolytic cells, which occur only with the input of an external energy source, E cell is negative because they are nonspontaneous.

Philipp_V_Dis1K
Posts: 32
Joined: Fri Sep 28, 2018 12:20 am

Re: Positive vs Negative E value

Postby Philipp_V_Dis1K » Wed Feb 20, 2019 2:16 pm

The E value does not depend on the right or left, it is on the E potential of the cathode and anode.

daniella_knight1I
Posts: 57
Joined: Fri Sep 28, 2018 12:18 am

Re: Positive vs Negative E value

Postby daniella_knight1I » Wed Feb 20, 2019 2:40 pm

The e value will depend on the overall value of the cell which you get by adding the two half-reactions together to get the overall value.

Katelyn Pham 4E
Posts: 30
Joined: Fri Sep 28, 2018 12:21 am

Re: Positive vs Negative E value

Postby Katelyn Pham 4E » Wed Feb 20, 2019 3:15 pm

Ecell = Cathode(right)-Anode(left) and this is found from the half oxidation and reduction equations.


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