જો ${{\text{K}}_{\text{a}}}{\text{ }} = {\text{1}}{\text{.8}} \times {\text{1}}{{\text{0}}^{{\text{ - 5}}}}\,\,\,\,\,\,\,\,p{K_a} = 4.75$
$ = 7 + \frac{1}{2} \times 4.75 + \frac{1}{2}\log 1.8 \times {10^{ - 2}} = \,\,7 + 2.37 - 0.87 = 8.5$