Positive or Negative Ecell Values


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Theodore_Herring_1A
Posts: 60
Joined: Fri Sep 28, 2018 12:29 am

Positive or Negative Ecell Values

Postby Theodore_Herring_1A » Sat Mar 16, 2019 9:35 pm

How do you know if the Ecell should be positive or negative? For example, in galvanic cells, Ecell should be positive, but in other cells it is negative. What part of the question gives you this information?

Maayan Epstein 14B
Posts: 39
Joined: Fri Sep 28, 2018 12:20 am

Re: Positive or Negative Ecell Values

Postby Maayan Epstein 14B » Sat Mar 16, 2019 9:54 pm

Do you mean Ecell or E (standard) cell? Because E (with the circle on the top symbolizing standard conditions) is different from Ecell.
The Nernst equation shows the relationship between these: Ecell = E(standard) - (R*T)/(n*F) * lnQ

I hope that helps!

Priscilla Okaiteye
Posts: 61
Joined: Tue Nov 21, 2017 3:02 am

Re: Positive or Negative Ecell Values

Postby Priscilla Okaiteye » Sat Mar 16, 2019 10:02 pm

Ecell in electrocytic cells can be pos or neg, but also I have noticed in the textbook that there are a couple of problems where Ecell was pos for Galvanic cells. Usually, the value is supposed to be pos for Galvanic.

Cade Okohira 4K
Posts: 47
Joined: Fri Sep 28, 2018 12:15 am

Re: Positive or Negative Ecell Values

Postby Cade Okohira 4K » Sun Mar 17, 2019 6:49 pm

In galvanic cells, the cell potential must be positive for the travel of electrons and for the electric current to travel through the system. If the cell potential is negative, then the electric current won't travel through.

katie_sutton1B
Posts: 61
Joined: Fri Sep 28, 2018 12:17 am

Re: Positive or Negative Ecell Values

Postby katie_sutton1B » Sun Mar 17, 2019 7:26 pm

Also, a positive E means a -delta G, which is a spontaneous reaction. This comes from the equation deltaG=-nFE


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