rxn gibbs free energy






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705121606
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Joined: Wed Sep 18, 2019 12:17 am

rxn gibbs free energy

Postby 705121606 » Wed Feb 19, 2020 1:02 am

How is the reaction gibbs free energy (calculated using delta g= -rtlnk = rtlnQ) different from the gibbs free energy we calculated last week?
And can someone explain why it would form products when positive and reactants when negative? Is it also spontaneous only if it is positive?

Justin Sarquiz 2F
Posts: 106
Joined: Fri Aug 30, 2019 12:15 am

Re: rxn gibbs free energy

Postby Justin Sarquiz 2F » Wed Feb 19, 2020 8:23 am

When delta G is negative, the reaction is spontaneous, so it forms products because the reaction proceeds normally. When delta G is positive, the reaction is not spontaneous, so it forms reactants since the reaction does not proceed without an input of energy.

Tai Metzger 3K
Posts: 103
Joined: Sat Aug 24, 2019 12:17 am

Re: rxn gibbs free energy

Postby Tai Metzger 3K » Wed Feb 19, 2020 12:07 pm

When Q is greater than 1, delta G is positive and thus the rxn is not spontaneous in that direction. When Q is less than 1, delta G is negative and thus the rxn is spontaneous in that direction.

Viviana Velasquez
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Joined: Sat Jul 20, 2019 12:15 am

Re: rxn gibbs free energy

Postby Viviana Velasquez » Wed Feb 19, 2020 12:13 pm

For a reaction to be spontaneous, delta G has to be negative. When delta G is negative, it means the forward reaction is favored and products are formed. When delta G is positive, the opposite happens and reactants are formed.

Brianna Becerra 1B
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Joined: Fri Aug 02, 2019 12:16 am

Re: rxn gibbs free energy

Postby Brianna Becerra 1B » Wed Feb 19, 2020 12:17 pm

The delta G calculated last week is delta G naught or the change in Gibb's Free Energy under standard conditions. We were first taught to calculate this using Delta H naught - T x Delta S naught. This week, we learned how to calculate the same change in Gibbs Free Energy under standard conditions through Delta G naught = - RTlnK. We also learned how to calculate the change in Gibbs free energy through: Delta G = Delta G naught + RTlnQ. It is important to note that delta G and delta G naught are different causing their calculations to vary as well.

Brandon Valafar
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Re: rxn gibbs free energy

Postby Brandon Valafar » Wed Feb 19, 2020 2:37 pm

Delta G has to be negative for a reaction to be spontaneous. Therefore, when delta G is negative, it means products are formed. When delta G is positive the reaction is not spontaneous and reactants are formed.


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