### Spontaneity and Entropy

Posted:

**Mon Feb 10, 2020 10:17 am**What is the relationship between entropy and spontaneous reactions? Does it always depend on the Gibbs free energy equation?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=131&t=58948

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Posted: **Mon Feb 10, 2020 10:17 am**

What is the relationship between entropy and spontaneous reactions? Does it always depend on the Gibbs free energy equation?

Posted: **Mon Feb 10, 2020 10:34 am**

Spontaneity is determine using the Gibbs Free energy equation G=H-TS. Since -G is spontaneous, we want a large and positive delta S. However, you would need to plug in the values for temperature and enthalpy to really determine spontaneity because enthalpy could be greater than TS.

Posted: **Mon Feb 10, 2020 11:03 am**

An increase in entropy leads to a decrease in Gibbs free energy. Both these situations represent a spontaneous reaction

Posted: **Mon Feb 10, 2020 11:18 am**

This question can also be considered more conceptually using the second law of thermodynamics. Since the entropy of the universe is always increasing, you can think of processes that increase entropy as naturally occurring, or spontaneous. However, whether or not delta G is actually negative depends on the magnitude of delta S relative to delta H.