pH of acid or base mixtures

Exercise 1

Determine the $pH$ of the solution obtained by mixing $V_1$ = 350 $mL$ $HI$ 0.65 $M$ with $V_2$ = 150 $mL$ $HNO_3$ 0.55 $M$

$HI$ ,$ HNO_3$ :    strong acids $n_{HI}$ $=$ $c_{HI}\cdot V_1$ = 0.2275 $mol$ $n_{HNO_3}$ $=$ $c_{HNO_3}\cdot V_2$ = 0.0825 $mol$ $pH$ $=$ $-log\frac{n_{HI} + n_{HNO_3}}{V_1+V_2}$ = 0.208