Chemistry - Ionic Equilibrium Question with Solution | TestHub

Given:

Concentration of salt = $0.010M$

pH = $4$

Salt hydrolysis:

$Pu{O}_2^{2+}+H_{2}O\rightleftharpoons Pu{O}_{2}O{H}^{+}+H^{+}$

pH = $4$

$[H^{+}]=10^{-4}$

Initial concentration of salt = $0.01=10^{-2}M$

Let hydrolysis = $x$

$x=[H^{+}]=10^{-4}$

At equilibrium:

Species Conc.

$Pu{O}_2^{2+}$ $10^{-2}-10^{-4}$

$Pu{O}_{2}O{H}^{+}$ $10^{-4}$

$H^{+}$ $10^{-4}$

Hydrolysis constant:

$K_a=\frac{[Pu{O}_{2}O{H}^{+}][H^{+}]}{[Pu{O}_2^{2+}]}$

$K_a=\frac{10^{-4}\times 10^{-4}}{10^{-2}}$

$K_a=10^{-6}$

$p{K}_a=6$

For conjugate base:

$p{K}_a+p{K}_b=14$

$p{K}_b=14-6$

$p{K}_b=8$