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.

In summary, the Gibbs free energy change during a reaction depends on the concentrations of the reactants and products. It can be calculated using the equation ΔG = ΔG° + RTlnQ, and its sign indicates the direction in which the reaction is spontaneous. Understanding this relationship is crucial for predicting the behaviour of chemical reactions.