Question

15ml of 0.325M NaOH is delivered into 35ml HOBr solution of unknown concentration.The pH of the final solution is 7.48. Ka for HOBr is 2.0 x 10-9at 25C. Find the number of moles of OBr- and HOBr in the final solution.

Answer 1

I would use the Henderson-Hasselbalch equation to determine the ratio of base to acid. Assuming all of the NaOH is converted to base, then OBr^- will be moles NaOH and you can use the ratio from the HH equation to determine moles of the acid.