## Difference between delta S and delta S naught

$\Delta S = \frac{q_{rev}}{T}$

Mike Matthews 1D
Posts: 59
Joined: Fri Sep 29, 2017 7:04 am

### Difference between delta S and delta S naught

Could someone please explain in detail the difference between delta S and delta S naught. Why is it that delta S total can be used to indicate the spontaneity of a reaction while delta S naught cannot be used to indicate spontaneity?

Cooper1C
Posts: 50
Joined: Fri Sep 29, 2017 7:07 am

### Re: Difference between delta S and delta S naught

The third law of thermodynamics says that the total entropy is always increasing, so delta S total must be positive. The standard enthalpy for a reaction can be positive or negative depending on the reaction. For example, building polymers from monomers has a negative delta S (the complexity is increasing), but breaking down polymers to form monomers has a positive delta S (the complexity is decreasing).

Angela 1K
Posts: 80
Joined: Fri Sep 29, 2017 7:05 am

### Re: Difference between delta S and delta S naught

Cooper1C wrote:The third law of thermodynamics says that the total entropy is always increasing, so delta S total must be positive. The standard enthalpy for a reaction can be positive or negative depending on the reaction. For example, building polymers from monomers has a negative delta S (the complexity is increasing), but breaking down polymers to form monomers has a positive delta S (the complexity is decreasing).

Just a quick correction: the second law of thermodynamics states that the total entropy is always increasing. The third law states that the entropy of a perfect crystal at absolute zero is 0.