Step-wise approach to calculate pH of weak electrolyte
Write all the chemical equations involving dissociation. Balance them completely.
The reaction with higher (K_a) is the primary reaction while other is a subsidiary reaction.
Tabulate the following values of the concentrations of various species : initial concentration ‘c’, change in concentration as the reaction reaches equilibrium in terms of degree of dissociation, (alpha) and concentrations of equilibrium mixture.
Solve for (alpha) by solving the equilibrium constant equation for principal reaction.
Calculate the concentration of species using the value of (alpha) .
Calculate (pH) = -log([H_3O]^+)