Explain a general step-wise approach to evaluate the $pH$ of the weak electrolyte.

Step-$1$ : The species present before dissociation are identified as Bronsted-Lowry acid/base.

Step-$2$: Balanced equations for all possible reaction. i.e. with a species acting both as acid as well as base are written.

Step-$3$: The reaction with the higher $\mathrm{K}_{a}$ is identified as the primary reaction whilst the other is a subsidiary reaction.

Step-$4$: Enlist in a tabular form the following values for each of the species in the primary reaction. $(i)$ Initial concentration $c$, $(ii)$ Change in concentration on proceeding to equilibrium in term of $(\alpha)$, degree of ionization. $(iii)$ Equilibrium concentration.

Step-$5$ : Substitute equilibrium concentrations into equilibrium constant equation for principal reaction and solve for $\alpha$.

Step-$6$: Calculate the concentration of species in principal reaction.

Step-$7$: Calculate $\mathrm{pH}=-\log \left[\mathrm{H}_{3} \mathrm{O}^{+}\right]$.