Entropy & Gibbs Free Energy

Entropy is a measure of the disorder or randomness in a system. It quantifies the amount of energy in a physical system that is not available to do work.

Gibbs Free Energy (G) is a thermodynamic potential that measures the maximum reversible work obtainable from a thermodynamic system at constant temperature and pressure.

A reaction is spontaneous if the change in Gibbs Free Energy (ΔG) is negative (ΔG < 0).

When both enthalpy (ΔH) and entropy (ΔS) are positive, a high temperature is needed for the reaction to be spontaneous.

The entropy of the system decreases when a gas changes to a solid because the molecules become more ordered.

Increasing the number of moles of gas generally increases the entropy of the system due to greater disorder.

A negative enthalpy change (ΔH < 0) indicates that a reaction releases heat, making it exothermic.

A low temperature is required for a spontaneous reaction when both enthalpy and entropy are negative.

The formula for Gibbs Free Energy is ΔG = ΔH - TΔS, where ΔG is the change in Gibbs Free Energy, ΔH is the change in enthalpy, T is the temperature in Kelvin, and ΔS is the change in entropy.

If ΔG = 0, the system is at equilibrium, and there is no net change in the concentrations of reactants and products.