5.17

c=0,10mol/dm³

$\begin{array}{l|l} &\left[Al\left(H_2O\right)_6\right]^{3+}&H_2O&\left[Al\left(H_2O\right)_5OH^-\right]^{2+}&H_3O^+\\ \hline c_{alku}&0{,}10&-&0&0\\ muutos&-x&-&+x&+x\\ c_{tasap}&0{,}10-x&-&0{,}001&0{,}001 \end{array}$

pH=3,00

$10^{-3}=0{,}001$
$-\lg\left(0{,}001\right)=3$

$\left[H_3O^+\right]=0{,}001\ \frac{mol}{dm^3}$

$K_a=\frac{K_w}{K_b}=\frac{1{,}008\cdot10^{-14}}{0{,}001}=1{,}008\cdot10^{-11}\ \frac{mol}{dm^3}$
$pK_a=-\lg K_a=10{,}9965...\approx11$

protolysoitumisaste

$\frac{\left[H_3O^+\right]}{c\left(\left[Al\left(H_2O\right)_6\right]^{3+}\right)_{alku}}=\frac{0{,}001}{0{,}10}=0{,}01=1\%$