GIBB'S FREE ENERGY

Learning Objective 1: Describe Gibbs Free Energy

What is Gibbs Free Energy?

• Definition: The maximum available energy in a system that can perform useful work during a reaction.

• Formula:

  

  • ΔH: Change in enthalpy (heat content).

  • T: Absolute temperature (Kelvin).

  • ΔS: Change in entropy (disorder).

• Units: kJ/mol.

Key Points:

• ΔG < 0: Reaction is spontaneous (releases energy, exergonic).

• ΔG > 0: Reaction is non-spontaneous (requires energy, endergonic).

• ΔG = 0: Reaction is at equilibrium (no net energy change).

Importance in Chemistry:

• Helps predict the direction of a chemical reaction.

• Determines if a reaction occurs spontaneously.

• Provides insight into how reactions behave under different conditions (e.g., temperature, concentration).

Learning Objective 2: Describe Free Energy and the Roles of ATP

Free Energy in Reactions:

• Standard Free Energy Change (ΔG°): Free energy under standard conditions (1M concentration, 25°C, pH 7.0).

  

• R: Ideal gas constant (8.314 J/mol·K).

• [P] and [S]: Concentrations of products and reactants.

• Exergonic vs. Endergonic Reactions:

Role of ATP in Energy Transfer:

• ATP (Adenosine Triphosphate): Universal energy currency in cells.

• Structure: Contains two high-energy phosphate bonds.

• Hydrolysis of ATP:

  • Reaction:

• Releases energy to drive endergonic reactions.

• ATP-ADP Cycle: