## Test 2

$\Delta G^{\circ} = -nFE_{cell}^{\circ}$

Lauren Huang 1H
Posts: 60
Joined: Fri Sep 28, 2018 12:16 am

### Test 2

Can someone please explain why Gibbs free energy for the combustion of a gas used to heat a BBQ at a pool party is negative? Wouldn't it require be a non-spontaneous process for the combustion to occur?

Sapna Ramappa 1J
Posts: 63
Joined: Fri Sep 28, 2018 12:24 am

### Re: Test 2

The Gibbs free energy of the combustion of gas would be negative, as the reaction is exergonic. This is because gas will have more energy than the water and CO2 molecules released after the combustion, and thus the reaction will be spontaneous.

Abby-Hile-1F
Posts: 46
Joined: Fri Sep 28, 2018 12:16 am

### Re: Test 2

If the Gibbs Free energy of a rxn is lees than zero, then that means it will occur spontaneously.

Carissa Young 1K
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Joined: Fri Sep 28, 2018 12:17 am

### Re: Test 2

What happens if Gibbs free energy is zero exactly?

dgerges 4H
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Joined: Fri Sep 28, 2018 12:24 am

### Re: Test 2

a negative gibbs free energy means it is spontaneous, unlike a negative entropy which means its nonspontaneous

Tuong-Minh Tran 1C
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Joined: Fri Sep 28, 2018 12:19 am

### Re: Test 2

Carissa Young 1K wrote:What happens if Gibbs free energy is zero exactly?

When Gibbs free energy is zero, that means that the reaction is at equilibrium.

Yousif Jafar 1G
Posts: 59
Joined: Thu May 10, 2018 3:00 am

### Re: Test 2

Also if gibbs free energy is zero, the free energy of the reactants equals that of the products

Yvonne Du
Posts: 64
Joined: Fri Sep 28, 2018 12:23 am

### Re: Test 2

Since a combustion releases heat, you can therefore say that the reaction is exothermic and Gibbs free energy is negative

Dayna Pham 1I
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Joined: Fri Sep 28, 2018 12:16 am
Been upvoted: 3 times

### Re: Test 2

Lauren Huang 1H wrote:Can someone please explain why Gibbs free energy for the combustion of a gas used to heat a BBQ at a pool party is negative? Wouldn't it require be a non-spontaneous process for the combustion to occur?

This question confused me as well. After the test, I realized it was spontaneous because combustion itself is spontaneous, as it releases heat. Yes, the BBQ needs heat, but the heat is provided by the heat released from the combustion reaction.

lizettelopez1F
Posts: 29
Joined: Fri Sep 28, 2018 12:19 am

### Re: Test 2

Did anyone understand what delta G should be for the question from test 2 where it talks about photosynthesis of an old tree?

Subhani Diu 1F
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Joined: Fri Sep 28, 2018 12:20 am

### Re: Test 2

Delta G would be less than zero because combustion releases heat and is spontaneous.

Sheridan Slaterbeck 1J
Posts: 62
Joined: Fri Sep 28, 2018 12:27 am

### Re: Test 2

delta G is negative as a combustion will increase the entropy S, or disorder, of the system and is therefore spontaneous.

505211599
Posts: 60
Joined: Fri Sep 28, 2018 12:28 am

### Re: Test 2

Delta G is negative because the reaction is exergonic.