Acid & Base?

Question

How much 0.200M NaOH solution must be added to a 0.100M solution of HOBr (pH of 4.843 ) in order to change [H3O+] to 1X10^-7

Answer 1

From the given pH, you must work out the Ka value of HOBr.
Pure KOBr solution will have a pH of over 7, so pH=7 will be before the end point.

This is now a buffer solution question: [H+] = Ka x [acid]/[base].

Set [H+] to 1 x 10-7, and you are on your way!