EXAMPLE 1: Standardization of a NaOH Solution using KHP
An aqueous solution of sodium hydroxide (NaOH) was standardized by titrating it against a 0.1421 g sample of potassium hydrogen phthalate (KHP). (NOTE: The chemical formula of KHP is HKC₈H₄O₄.) The initial reading
taken from the buret containing the NaOH was 0.52 mL and the final volume reading was 32.86 mL.

What is the molarity of the NaOH solution?

The reaction equation is:
HKC₈H₄O₄ + NaOH -----> NaKC₈H₄O₄ + H₂O

Volume of NaOH used:
32.86 mL – 0.52 mL = 32.34 mL NaOH

Moles of KHP (HKC₈H₄O₄):
(0.1421 g KHP)( 1 mol KHP / 204.23 g KHP ) = 6.958 x 10^-4 mol KHP

Moles of NaOH neutralized:
(6.958 x 10^-4 mol KHP)(1 mol NaOH / 1 mol KHP) = 6.958 x 10^-4 mol NaOH

Molarity of NaOH:
6.958 x 10^-4 mol NaOH / 0.03234 L NaOH = 0.02152 M NaOH
 

EXAMPLE 2: Standardization of a H₂SO₄ Solution using KHP
In a second procedure, a 25.00 mL sample of H₂SO₄ was titrated with the standardized NaOH solution from Example 1. The reading taken from the NaOH buret before the titration was 0.36 mL and the final volume reading was 41.78 mL.

What is the molarity of the H₂SO₄?

The balanced equation involved in the neutralization is:
H₂SO₄ + 2 NaOH -----> Na₂SO₄ + 2 H₂O

Volume of NaOH used:
41.78 mL – 0.36 mL = 41.42 mL NaOH

Moles of NaOH used:
(0.04142 L NaOH)(0.02152 mol NaOH / 1 L NaOH) = 8.914 x 10^-4 mol NaOH

Moles of H₂SO₄ neutralized:
(8.914 x 10^-4 mol NaOH)(1 mol H₂SO₄ / 2 mol NaOH) = 4.457 x 10^-4 mol H₂SO₄

Molarity of H₂SO₄:
4.457 x 10^-4 mol H₂SO₄ / 0.02500 L H₂SO₄ = 0.01783 M H₂SO₄