H2SO4(aq) + 2NaOH(aq) → Na2SO4(aq) + 2H2O(l)

Question

A solution of 0.178 NaOH is used to neutralize 25 mL H2SO4 solution.

If 32.8 mL NaOH solution is required to reach the endpoint, what is the molarity of the H2SO4 solution?

Answer 1

Neutralization of an acid (H₂SO₄) and a base (NaOH)

H₂SO₄(aq) + 2 NaOH(aq) ==> Na₂SO₄(aq) + 2H₂O(l) ... note the 2:1 mol ratio of base to acid

moles NaOH used = 32.8 ml x 1 L/1000 ml x 0.178 mol/L = 0.005838 moles

moles H₂SO₄ present = 0.005838 mol NaOH x 1 mol H₂SO₄/2 mol NaOH = 0.002919 mol H₂SO₄

Molarity H₂SO₄ = 0.002919 moles/0.025 L = 0.1168 M = 0.117 M (to 3 signifiant figures)