# Difference between G and G(o)

Gold Member

## Homework Statement

What is the Difference between delta G and delta G°?
I have encountered them in various equations but their exact meaning and difference is never mentioned.°

mjc123
Homework Helper
ΔG° is the value of ΔG with all reagents in their standard states. You ought to have encountered this definition in your study of thermodynamics.
For example, if ΔG is the free energy change for a reaction in a system described by the reaction quotient Q (have you come across this?), then
ΔG = ΔG° + RTlnQ
At equilibrium Q = Keq and ΔG = 0, so
ΔG° + RTlnKeq = 0

Gold Member
ΔG° is the value of ΔG with all reagents in their standard states. You ought to have encountered this definition in your study of thermodynamics.
For example, if ΔG is the free energy change for a reaction in a system described by the reaction quotient Q (have you come across this?), then
ΔG = ΔG° + RTlnQ
At equilibrium Q = Keq and ΔG = 0, so
ΔG° + RTlnKeq = 0
Yes I have come across this, but didn't realize the exact difference. Thank you for the clarification :D