A 20.0 mL solution of NaOH is neutralized with 32.5 mL of 0.200 M HBr. What is the concentration of the original NaOH solution?

Answer 1

First, find the number of mols of HBr used for the neutralization by multiplying the concentration of HBr by the volume of HBr (in liters)...

0.200M * 0.0325L = 6.5E-3 mol HBr

Since the reaction between HBr and NaOH is one-to-one, you know that there must have been 6.5E-3 mol NaOH in the basic 20.0mL solution, so to get concentration, divide the moles of base by the volume of the base (in liters) and you get...

6.5E-3mol/0.0200L = 0.325M NaOH