Hello!
To solve this exercise, we will use the Henderson-Hasselbach equation, applying the values for each Concentration and the pKa:
[tex]pH=pKa + log ( \frac{[KBrO]}{[HBrO]} )=8,67 + log ( \frac{0,64 M}{0,90 M} )=8,54[/tex]
So, the pH for this solution of NaBrO and HBrO would be 8,54
Have a nice day!
