d
\( {\text{pH}} = {\text{7}} + \frac{{\text{1}}}{{\text{2}}}p{K_a} + \frac{1}{2}\log C = 7 + \frac{1}{2} \times 7 + \frac{1}{2}\log {10^{ - 3}} = 7 + \frac{7}{2} - \frac{3}{2}\log 10 \)

                               \(= \frac{{14 + 7 - 3}}{2} - \frac{{21 - 3}}{2} = \frac{{18}}{2} = 9\)

\({\text{h}} = \sqrt {\frac{{{{\text{K}}_{\text{h}}}}}{{\text{C}}}}  = \sqrt {\frac{{{K_w}}}{{{K_a} \times C}}}  = \sqrt {\frac{{{{10}^{ - 14}}}}{{{{10}^{ - 7}} \times {{10}^{ - 3}}}}}  = \sqrt {{{10}^{ - 14}} \times {{10}^{10}}}  = \sqrt {{{10}^{ - 4}}}  = {10^{ - 2}}\)

\([O{H^ - }] = \sqrt {\frac{{{K_w} \times C}}{{{K_a}}}}  = \sqrt {\frac{{{{10}^{ - 14}} \times {{10}^{ - 3}}}}{{{{10}^{ - 7}}}}}  = \sqrt {{{10}^{ - 17}} \times {{10}^{ - 7}}}  = \sqrt {{{10}^{ - 10}}}  = {10^{ - 5}}\)