## How to tell what happens to entropy by seeing a reaction?

Fenared Ortiz 3K
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Joined: Wed Nov 16, 2016 3:03 am

### How to tell what happens to entropy by seeing a reaction?

C12H22O11(s) + O2(g) ---> CO2(g) +H2O(l)

Given this equation how would we be able to tell what happens to entropy?

Andy Nguyen 1A
Posts: 56
Joined: Thu Jul 27, 2017 3:00 am

### Re: How to tell what happens to entropy by seeing a reaction?

Normally, combustion reactions result in an increase in entropy. Based on the phase changes, we see that a solid changed into a gas and liquid, which means an increase in entropy.

Sue Xu 2K
Posts: 58
Joined: Fri Sep 29, 2017 7:06 am

### Re: How to tell what happens to entropy by seeing a reaction?

You can just generally look at the phase of the phase of the reactants and products. In this reaction, the reactants are 1 solid and 1 gas, while the products are 1 liquid and 1 gas. Because liquid has higher entropy than solid, the entropy of the products is higher.

Cynthia Tsang
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Joined: Fri Sep 29, 2017 7:07 am
Been upvoted: 1 time

### Re: How to tell what happens to entropy by seeing a reaction?

Like mentioned above, since the entropy of the products is higher, the total entropy would be a positive value.

David Minasyan 1C
Posts: 54
Joined: Thu Jul 13, 2017 3:00 am

### Re: How to tell what happens to entropy by seeing a reaction?

Generally speaking, the entropy for gas > liquid > solid.

Phillip Winters 2F
Posts: 50
Joined: Fri Sep 29, 2017 7:05 am

### Re: How to tell what happens to entropy by seeing a reaction?

The phase of the reactants and products are the best way of looking at a reaction and determining how entropy changes, and entropy increases from solid to liquid to gas

Garret G 2F
Posts: 24
Joined: Fri Sep 29, 2017 7:06 am

### Re: How to tell what happens to entropy by seeing a reaction?

This youtube does a really good job of explaining how to predict changes in entropy: https://www.youtube.com/watch?v=ro3AnXdajAM

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