What do you understand by:
(i) Standard free energy change (∆rG0)
(ii) Standard free energy of formation (∆fG0).
(i) Standard free energy change (∆G0): It is defined as ‘the free energy change for a process at 298K in which the reactants in their standard states are converted into the products in their standard states’. Thus,
The value of ∆G0 for a reaction can be derived from the standard free energies of formation (∆fG0).
(ii) Standard free energy of formation (∆fG0) of a compound is defined as ‘the change in free energy when 1 mole of a compound is formed from its constituent elements in their standard states”. Thus,
= [Sum of the standard free energies of formation of products] - [Sum of the standard free energies of formation of reactants]
It may be pointed here that ‘the standard free energy of formation of an element in its standard state is zero’.
