Free Energy and Equilibrium Constant

Rucete ✏ Chemistry In a Nutshell

1. Gibbs Free Energy and Spontaneity

• Gibbs Free Energy (ΔG) indicates whether a chemical reaction is spontaneous.
• ΔG < 0 → Reaction is spontaneous
• ΔG > 0 → Reaction is non-spontaneous
• ΔG = 0 → Reaction is at equilibrium

2. Key Equations

Standard-State Free Energy and Equilibrium Constant:

ΔG° = –RT lnK

Free Energy at Non-Standard Conditions:

ΔG = ΔG° + RT lnQ

Where:

• ΔG = free energy
• ΔG° = standard-state free energy
• R = ideal gas constant = 8.314 J/mol·K
• T = temperature in Kelvin
• Q = reaction quotient
• K = equilibrium constant

3. Relationship Between ΔG° and K

ΔG°	K	Interpretation
ΔG° < 0	K > 1	Products are favored at equilibrium
ΔG° > 0	K < 1	Reactants are favored at equilibrium
ΔG° = 0	K = 1	System is at equilibrium

In a nutshell

Negative G means Go!

• ΔG° < 0 → K > 1 → Products favored
• ΔG° > 0 → K < 1 → Reactants favored
• ΔG° = 0 → K = 1 → Equilibrium