Question

A 25.0 ml aliquot of an HCl solution of unknown concentration is pipetted into a 125 ml Erylemeyer flask. Three drops of indicator are added and the resulting solution is titrated to the endpoint with 35.0 ml of 0.1005 M NaOH. What is the molar concentration of the aliquot? (SHOW ALL WORK)

Answer 1

The reaction:
HCl + NaOH = NaCl + H2O
The ratio of HCl/NaOH is 1:1, so:
VHCl ∙ CHCl = VNaOH ∙ CNaOH,
where V - volume and C - molar concentration
Therefore:
CHCl = (VNaOH ∙ CNaOH) / VHCl = (35.0 ∙ 0.1005) / 25.0 = 0.1407
Answer:
0.1407 M