pH of acid or base mixtures

Exercise 3

   

Determine the $pH$ of the solution obtained by mixing $V_1=$ 200 $mL \; HCl $ 0.45 $M$ with $V_2=$ 450 $mL \;$ A$lCl_3 $ 0.5 $M$

$HCl$  strong acid , $Αl(H_2O)_6^{3+}$ : weak acid $n_{HCl}$ $=$ $c_{HCl}\cdot V_{HCl}$ = 0.09 mol $pH$ $=$ $14$ $+$ $log\frac{n_{HCl}}{V_1+V_2}$ = 0.859