(a)[1]
Write an expression for the $K_a$ of the weak acid HA using the concentrations of the species present.
(b(i))[2]
The hydroxylammonium ion, $\\text{HONH}_3^+$, behaves as a weak acid. A $1.00 \\times 10^{-3}\\,\\text{mol dm}^{-3}$ solution of hydroxylammonium ions has a pH of $4.41$. Calculate the $K_a$ of $\\text{HONH}_3^+$.
(b(ii))[1]
Calculate the $\\text{p}K_a$ value for $\\text{HONH}_3^+$.
(c)[2]
The solubility product of manganese(II) hydroxide, $\\text{Mn(OH)}_2$, in water is $1.1 \\times 10^{-11}\\,\\text{mol}^3\\,\\text{dm}^{-9}$ at $298\\,\\text{K}$. Calculate the solubility of $\\text{Mn(OH)}_2$ in water at $298\\,\\text{K}$.