Thermochemistry is a branch of chemistry that deals with the study of the heat energy involved in chemical reactions and processes. It involves the measurement and calculation of changes in enthalpy, entropy, and Gibbs free energy.
Delta G, also known as Gibbs free energy, is a thermodynamic quantity that represents the amount of energy available to do work in a chemical reaction. It is a measure of the spontaneity of a reaction and can be calculated using the equation ΔG = ΔH - TΔS, where ΔH is the change in enthalpy, T is the temperature in Kelvin, and ΔS is the change in entropy.
Delta G is related to equilibrium by the equation ΔG = -RTlnK, where R is the gas constant and K is the equilibrium constant. When ΔG is negative, the reaction is spontaneous and will proceed towards the products. When ΔG is positive, the reaction is non-spontaneous and will proceed towards the reactants. When ΔG is zero, the reaction is at equilibrium.
Delta G can be calculated experimentally using calorimetry, which measures the heat change in a reaction, and then using the equation ΔG = ΔH - TΔS. Alternatively, it can be calculated from standard enthalpy and entropy values using the equation ΔG° = ΔH° - TΔS°. These values can be found in tables or calculated using Hess's Law.
The value of Delta G is affected by temperature, pressure, and the concentrations of reactants and products. It is also affected by the nature of the reaction, such as whether it is exothermic or endothermic, and the number of moles of gas involved. Changes in these factors can lead to changes in the value of Delta G and thus affect the spontaneity of a reaction.