Spontaneous reactions

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705121606
Posts: 68
Joined: Wed Sep 18, 2019 12:17 am

Spontaneous reactions

Postby 705121606 » Sat Feb 08, 2020 10:13 pm

I know that having a negative delta g tells us that the reaction is spontaneous. When we are looking at delta s the total change in entropy being positive would also tell us the reaction would be spontaneous. Is this because a large delta s is being subtracted from delta h making delta g more negative?

Aarja Pavade 1H
Posts: 103
Joined: Sat Aug 17, 2019 12:18 am

Re: Spontaneous reactions

Postby Aarja Pavade 1H » Sat Feb 08, 2020 10:20 pm

If delta S is larger than delta H, it would make delta G negative (spontaneous). However, we would need to know the exact values for this. Another situation in which the reaction is spontaneous is if delta H is negative and delta S is positive. Subtracting a positive from a negative gives us a negative value for delta G, showing that the reaction is spontaneous. This situation doesn't require exact walls and is more general.

Renee Grange 1I
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Re: Spontaneous reactions

Postby Renee Grange 1I » Sat Feb 08, 2020 10:58 pm

We can only tell if a reaction is spontaneous based on delta S alone is delta S total > 0. This is because spontaneous reactions follow the second law of thermodynamics, which is that entropy is always increasing. If delta S total is > 0, entropy is increasing and the reaction is spontaneous.

BritneyP- 2c
Posts: 101
Joined: Sat Sep 14, 2019 12:15 am

Re: Spontaneous reactions

Postby BritneyP- 2c » Sat Feb 08, 2020 11:00 pm

Having a larger delta S would make delta G smaller meaning it is spontaneous. If the delta S x T is still smaller than H, then that means the delta G is positive and not spontaneous, which is not favorable.


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