How does Gibbs free energy change with concentration during a reaction?

During a reaction, the Gibbs free energy changes with concentration as it depends on the reactant and product concentrations.

The Gibbs free energy (G) is a thermodynamic potential that measures the maximum reversible work that a system can perform at constant temperature and pressure. It is a state function, meaning its value depends only on the state of the system and not on how the system arrived at that state. In the context of a chemical reaction, the Gibbs free energy change (ΔG) is related to the concentrations of the reactants and products.

The relationship between Gibbs free energy and concentration is given by the equation ΔG = ΔG° + RTlnQ, where ΔG° is the standard Gibbs free energy change, R is the gas constant, T is the temperature in Kelvin, and Q is the reaction quotient. The reaction quotient Q is a measure of the relative concentrations of the products and reactants at any point in time during the reaction.

When the reaction is at equilibrium, Q equals the equilibrium constant K, and ΔG equals zero. This is because at equilibrium, there is no net change in the system, so no work can be done. If Q is less than K (meaning there are more reactants than products), ΔG is negative, indicating that the reaction is spontaneous in the forward direction. Conversely, if Q is greater than K (meaning there are more products than reactants), ΔG is positive, indicating that the reaction is non-spontaneous in the forward direction and spontaneous in the reverse direction.

To understand how a system responds to changes in concentration or other conditions, exploring Le Châtelier’s Principle can provide deeper insight. This principle explains the system's response to disturbances, which is directly relevant to understanding Gibbs free energy changes.

IB Chemistry Tutor Summary: The Gibbs free energy change (ΔG) during a reaction is influenced by the concentrations of reactants and products. It's calculated with the formula ΔG = ΔG° + RTlnQ. A negative ΔG suggests a spontaneous reaction, while a positive one indicates non-spontaneity. At equilibrium, ΔG is zero, showing no net change in the system.