During a titration, 25 mL of 0.03 M H₂SO₄ is titrated with 0.05 M NaOH using phenolphthalein as the indicator. Determine the volume of NaOH required to reach the endpoint.

Step-by-step solution

1. Recognise H₂SO₄ as a diprotic acid; each mole provides 2 mol of H⁺.
2. Compute moles of H₂SO₄: $0.03\text{ M}\times 0.025\text{ L}=0.00075\text{ mol}$.
3. Find total moles of H⁺: $0.00075\text{ mol}\times 2=0.0015\text{ mol}$.
4. Use 1:1 stoichiometry with NaOH: moles NaOH needed = $0.0015$ mol.
5. Determine volume of 0.05 M NaOH: $\frac{0.0015\text{ mol}}{0.05\text{ M}}=0.030\text{ L}=30\text{ mL}$.
6. Phenolphthalein changes colour at pH ≈10, matching the endpoint for this titration.

Concept tested: Titration of diprotic acid

Published 10 October 2026 · How this solution was prepared and checked