# Gibbs free energy various forms

## Main Question or Discussion Point

What is the difference between 1) ΔG°' and ΔG°
and 2) ΔG°' and ΔG ?
ΔG° I think it is the gibbs free energy at standard state means at room temperature 1 atm pressure.

## Answers and Replies

Titan97
Gold Member
##\Delta G^0## is constant at all conditions. Its ##\Delta G## that changes with change in conditions.

What about ΔG°' ?

Titan97
Gold Member
Where did you read it?

It was given in the question of our assignment.

May be something like the conditions that are common in your field of science, say pH is 7 and temp is 36 °C.

Chestermiller
Mentor
What is the difference between 1) ΔG°' and ΔG°
and 2) ΔG°' and ΔG ?
ΔG° I think it is the gibbs free energy at standard state means at room temperature 1 atm pressure.
ΔG0 is the change in free energy between state 1 and state 2, where

State 1: Stoichiometric quantities of pure reactants in separate containers, each at temperature T and 1 atm pressure

State 2: Corresponding stoichiometric quantities of pure products in separate containers, each at temperature T and 1 atm pressure

So ΔG0 is a function of temperature.

Chet

Chestermiller
Mentor
##\Delta G^0## is constant at all conditions. Its ##\Delta G## that changes with change in conditions.
What do the words "ΔG° I think it is the gibbs free energy at standard state means at room temperature 1 atm pressure." mean to you?

Chet

Chestermiller
Mentor
I've never seen ΔG0' used before, but, apparently ΔG0' is the value of ΔG0 at 25 C (see post #7).

Incidentally, regarding ΔG, this is the change in free energy if the pressures of the pure species in States 1 and 2 (see post #7) are not all equal to 1 atm.

Chet