Concept of standard free energy of reactions

First law of thermodynamics states that , “ Energy can neither be created nor destroyed but can be changed from one form to another.”

a. Gibbs free energy : The amount of energy which is capable of doing work during a reaction at constant temperature and pressure is called Gibbs free energy.

Value of ΔG = -ve ( Exothermic)

Value of ΔG = +ve ( Endothermic)

b. Enthalpy: Heat content of reacting system is known as enthalpy.

ΔH = -ve ( Exothermic)

ΔH = +ve ( Endothermic)

c. Entropy: Degree of randomness of a system is known as entropy. Denoted by ‘S’.

ΔG = ΔH – TΔS