a
\({\text{x}} = \sqrt {\frac{{{{\text{K}}_{\text{w}}}}}{{{{\text{K}}_{\text{a}}} \times C}}} \,\,\,\,\,\,\,\,{K_w} = {10^{ - 14}}\,,\,\,\,{K_a} = 1.3 \times {10^{ - 9}},\,\,\,\,\,C = \frac{N}{{100}} = 0.01\)

\(x = \sqrt {\frac{{{{10}^{ - 14}}}}{{1.3 \times {{10}^{ - 9}} \times 0.01}}}  = 2.772 \times {10^{ - 2}}\)

\(\% = 2.77 \times  10^{-2} \times  100 = 2.77\%\)

\(K_a = 1.3 \times  10^{-9}\)

\(pK_a = 8.8\)

\(pH = 7 + \frac{1}{2}p{K_a} + \frac{1}{2}\log C\,\,\,\, \Rightarrow \,\,\,\,pH = 7 + \frac{1}{2} \times 8.8 + \frac{1}{2}\log {10^{ - 2}} = \,\,7 + 4.4 - 1.00 = 10.4\)