It becomes necessary to know what fraction of the initial amount of the reactants are converted into products at equilibrium.
The fraction of the initial molecules that are converted at equilibrium is called the degree of Dissociation/ionization.
Degree of dissociation or ionization = α = (Number of reactant molecules dissociated\ionized at the start)/(Number of reactant molecules at the start)
Degree of dissociation in Ionic equilibrium can be expressed in percentage.
% Degree of dissociation or ionization = α = (Number of reactant molecules dissociated or ionized at the start)/(Number of reactant molecules at the start) × 100