What is the concentration of the H2SO4 solution?

Question

20.0020.00 mL of a H₂SO₄ solution with an unknown concentration was titrated to a phenolphthalein endpoint with 35.7135.71 mL of a 0.12070.1207 M NaOH solution.

Answer 1

The balanced equation for titration of H2SO4 with NaOH is

H2SO4 + 2NaOH ==> Na2SO4 + 2H2O

If you find the moles of NaOH used, we can use the 2:1 mol ratio of NaOH:H2SO4 to find moles H2SO4.

Once we know moles H2SO4, we simply divide the moles by liters of H2SO4 to find concentration.

moles NaOH used = 35.71 mls x 1 L / 1000 mls x 0.1207 mol / L = 4.310x10^-3 mol NaOH

moles H2SO4 present = 4.310x10^-3 mol NaOH x 1 mol H2SO4 / 2 mol NaOH = 2.155x10^-3 mol

Concentration of H2SO4 = 2.155x10^-3 mol / 20.00 ml x 1000 ml / L = 0.1076 mol / L