Page 1 of 1

Gibbs = 0

Posted: Mon Feb 12, 2018 1:53 am
by JennyCKim1J
When is Gibbs free energy equal to zero?

For this question:

The entropy of vap of water is 109.0J/mol*K. What is the enthalpy of vap of water at its normal boiling point of 100 degree C?

Why do we set G equal to zero?

Re: Gibbs = 0

Posted: Mon Feb 12, 2018 2:21 am
by Nha Dang 2I
deltaG=0 when the reaction is at equilibrium, so for that problem, it's because it's at a phase change.

Re: Gibbs = 0

Posted: Mon Feb 12, 2018 2:18 pm
by Matthew Lin 2C
Yes you set deltaG equal to 0 when the reaction is at equilibrium, and you do it in this case because H20 is changing from liquid to vapor and vapor to liquid at equal rates at 100 degrees C (its normal boiling point).