Signs of delta G and E


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Peter Nguyen 2I
Posts: 61
Joined: Fri Sep 28, 2018 12:29 am

Signs of delta G and E

Postby Peter Nguyen 2I » Sun Feb 24, 2019 9:25 pm

For a spontaneous reaction, why does delta G have to be - and E have to be +?

Michelle Wang 4I
Posts: 63
Joined: Fri Sep 28, 2018 12:27 am

Re: Signs of delta G and E

Postby Michelle Wang 4I » Sun Feb 24, 2019 9:27 pm

A spontaneous reaction releases free energy, so delta G would be negative.

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

Re: Signs of delta G and E

Postby Angel Chen 2k » Mon Feb 25, 2019 1:25 am

For a spontaneous reaction, you usually have to look for values of delta H, delta S and T and results in a negative delta G value. With the Gibbs free energy equation, one of the factors for a reaction to be spontaneous is having a negative delta G.

Aarti K Jain 1L
Posts: 30
Joined: Fri Sep 28, 2018 12:20 am

Re: Signs of delta G and E

Postby Aarti K Jain 1L » Mon Feb 25, 2019 12:37 pm

As was said previously, in a spontaneous reaction, delta G is negative as free energy is released in the reaction. Also, DeltaG = -nFE, which means that for delta G to be negative, E must be positive. The standard potential is relative to electron-pulling power of the cathode, which means that if the cathode has a high positive potential, it call pull the electrons more easily, allowing the transfer of electrons to occur.

Karishma_1G
Posts: 67
Joined: Fri Sep 28, 2018 12:18 am

Re: Signs of delta G and E

Postby Karishma_1G » Mon Feb 25, 2019 1:36 pm

For all spontaneous reactions delta G is negative. Therefore, using the Delta G = -nFE equation, we find that E has to be positive for Delta G to be negative. This is because F (Faraday's Constant) is a positive number and n (moles of electrons transferred during the reaction) will also be positive. So, since there is a negative sign in front of the equation, E must be positive in order for Delta G to be negative and thus also for the reaction to be spontaneous.


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