Consider \(100.0 \mathrm{~mL}\) of a solution of \(0.200 \mathrm{M} \mathrm{Na}_{2} \mathrm{~A}\), where \(\mathrm{A}^{2-}\) is a base with corresponding acids \(\mathrm{H}_{2} \mathrm{~A}\) \(\left(K_{\mathrm{a}}=1.0 \times 10^{-3}ight)\) and \(\mathrm{HA}^{-}\left(K_{\mathrm{a}}=1.0 \times 10^{-8}ight)\).

a. How much \(1.00 \mathrm{M} \mathrm{HCl}\) must be added to this solution to reach \(\mathrm{pH}=8.00\) ?

b. Calculate the \(\mathrm{pH}\) at the second stoichiometric point of the titration of \(0.200 \mathrm{M} \mathrm{Na}_{2} \mathrm{~A}\), with \(1.00 \mathrm{M} \mathrm{HCl}\).