Question

29.47 mL of a solution of the acid HBr is titrated, and 72.90 mL of 0.2500-M NaOH is required to reach the equivalence point. Calculate the original concentration of the acid solution.

Answer 1

The original concentration of the acid solution is 6.175 $\times$ 10^-4 mol / L.

Explanation:

Concentration is the ratio of solute in a solution to either solvent or total solution. It is expressed in terms of mass per unit volume

                        HBr + NaOH -----> NaBr + H2O

There is a 1:1 equivalence with acid and base.

Moles of NaOH = 72.90 $\times$ 10^-3 $\times$ 0.25

                          = 0.0182 mol.

[ HBr ] = moles of base / volume of a solution

          = 0.0182 / 29.47

          = 6.175 $\times$ 10^-4 mol / L.