b
\({K_a} = C{\alpha ^2}\,\,\,\, \Rightarrow \,\,\,{10^{ - 5}} = 10{\alpha ^2}\,\,\,\, \Rightarrow \,\,\,{\alpha ^2} = \frac{{{{10}^{ - 5}}}}{{10}}\,\,\,\, \Rightarrow \,\,\,{\alpha ^2} = {10^{ - 6}}\,\,\,\,\, \Rightarrow \,\,\,\,\alpha = {10^{ - 3}}\)
\([{H^ + }] = C\alpha = 10 \times {10^{ - 3}} = {10^{ - 2}}\)
\(pH = - \log [{H^ + }] = - \log [{10^{ - 2}}] = 2\)