You want to determine the concentration of a phosphoric acid (H3PO4) solution using a standardized 0.0995 M NaOH solution. 10.00 mL of the H3PO4 solution needed to be titrated with 22.85 mL of the standardized 0.0995M NaOH solution to reach the equivalence point. What is the concentration of the H3PO4 solution

Explanation:

H₃PO₄ + 3NaOH = Na₃PO₄ + 3 H₂O.

1 mole     3 mole

22.85 mL of the standardized 0.0995M NaOH solution will contain

.0995 x .02285 moles of NaOH

= 22.7357 x 10⁻⁴ moles of NaOH

3 moles of NaOH reacts with 1 mole of H₃PO₄

22.7357 x 10⁻⁴ moles of NaOH reacts with 1 x 22.7357 x 10⁻⁴  / 3 mole of H₃PO₄

= 7.5785 x 10⁻⁴ moles of H₃PO₄

7.5785 x 10⁻⁴ moles of H₃PO₄  is contained in 10 mL or 10⁻² L

molarity of H₃PO₄ solution = 7.5785 x 10⁻⁴ / 10⁻²

= 7.58 x 10⁻² M

= .0758 M .