negative sign


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Sophia Dinh 1D
Posts: 100
Joined: Thu Jul 25, 2019 12:15 am

negative sign

Postby Sophia Dinh 1D » Sat Mar 14, 2020 6:32 pm

why is there a negative sign in front of n in the standard Gibbs energy equation?

Jessa Maheras 4F
Posts: 121
Joined: Fri Aug 02, 2019 12:16 am

Re: negative sign

Postby Jessa Maheras 4F » Sat Mar 14, 2020 6:38 pm

I believe that there is a negative sign due to the loss of energy.

Indy Bui 1l
Posts: 99
Joined: Sat Sep 07, 2019 12:19 am

Re: negative sign

Postby Indy Bui 1l » Sat Mar 14, 2020 6:40 pm

I believe it has to do with the relationship between E and delta G. When E is positive, delta G should be negative meaning it is spontaneous.

Wilson 2E
Posts: 100
Joined: Sat Aug 17, 2019 12:18 am

Re: negative sign

Postby Wilson 2E » Sat Mar 14, 2020 6:41 pm

Energy = -work/Charge;
Rearrange this to get work = -E*Charge
From the Farraday's constant, Charge = n*F
Therefore work = -n*F*E
At constant temp and pressure, work max = deltaG
Therefore deltaG = -n*F*E

Philip
Posts: 100
Joined: Sat Sep 07, 2019 12:16 am

Re: negative sign

Postby Philip » Sat Mar 14, 2020 6:53 pm

I think it's to show that energy is release or loss

Ashley Alvarado 2C
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Joined: Sat Aug 17, 2019 12:16 am

Re: negative sign

Postby Ashley Alvarado 2C » Sat Mar 14, 2020 8:36 pm

delta G*= -nFE
w(max)=-nFE
The system is doing work, so energy leaves the system resulting in -w.

Jared_Yuge
Posts: 100
Joined: Sat Aug 17, 2019 12:17 am

Re: negative sign

Postby Jared_Yuge » Sat Mar 14, 2020 8:38 pm

When E is positive it is spontaneous, so delta G needs to be negative

Frankie Mele 3J
Posts: 93
Joined: Wed Sep 30, 2020 10:09 pm

Re: negative sign

Postby Frankie Mele 3J » Mon Feb 22, 2021 7:42 pm

Favorable redox reactions have positive voltage differences which results in E being a positive value and deltaG therefore being negative.

Lesly Lopez 3A
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Re: negative sign

Postby Lesly Lopez 3A » Mon Feb 22, 2021 7:47 pm

The negative sign is important because it is telling you that the reaction has released or lost energy. The relationship between E and
G is that when E is positive, G should be negative meaning the reaction is spontaneous.

Samantha Lee 1A
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Joined: Wed Sep 30, 2020 10:05 pm
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Re: negative sign

Postby Samantha Lee 1A » Tue Feb 23, 2021 9:01 am

Yes! There is a negative sign in front of the n. The equation is

When the reaction is spontaneous, the is negative and is positive. In order for that to occur, there must be a negative sign in the equation.

Kimiya Aframian IB
Posts: 120
Joined: Wed Sep 30, 2020 9:34 pm

Re: negative sign

Postby Kimiya Aframian IB » Tue Feb 23, 2021 9:03 am

Sophia Dinh 1D wrote:why is there a negative sign in front of n in the standard Gibbs energy equation?

Hi! I think the negative sign in front of the n (mole value) is because it keeps the relationship between E, delta G, and spontaneity consistent. By this I mean that we need the E value to be positive when delta G is negative. Hope this helps!

Dominic Benna 2E
Posts: 93
Joined: Wed Sep 30, 2020 10:09 pm

Re: negative sign

Postby Dominic Benna 2E » Tue Feb 23, 2021 9:17 pm

A spontaneous reaction has a positive delta E, yet a negative delta G. So, in order to relate the two to each other, the negative sign is added.

Edison Tham 3D
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Joined: Mon Jun 17, 2019 7:25 am
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Re: negative sign

Postby Edison Tham 3D » Tue Feb 23, 2021 10:47 pm

The system is doing work and based on the fact that ∆G = maximum work, this would mean that there would be a negative sign.


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