### Delta G at boiling point

Posted:

**Tue Feb 26, 2019 11:10 pm**Why is standard Gibbs free energy for the vaporization of water at 100 degrees Celsius 0?

Created by Dr. Laurence Lavelle

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

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=135&t=43199

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Posted: **Tue Feb 26, 2019 11:10 pm**

Why is standard Gibbs free energy for the vaporization of water at 100 degrees Celsius 0?

Posted: **Wed Feb 27, 2019 11:46 am**

This is assuming constant temperature and pressure. Sooooooooooooooooo....:

del(S) = q/T = del(H)/T

T * del(S) = T * del(H)/T = del(H)

del(G) = del(H) - T * del(S) = del(H) - del(H) = 0

Hope that helps!

del(S) = q/T = del(H)/T

T * del(S) = T * del(H)/T = del(H)

del(G) = del(H) - T * del(S) = del(H) - del(H) = 0

Hope that helps!

Posted: **Wed Feb 27, 2019 1:22 pm**

It is 0 because water vaporizes at 100 degrees, therefore, the system is technically in equilibrium because the question asks for the delta g of vaporization.