Question

If a 25.0mL sample of sulphuric acid is titrated with 50.0mL of 0.025M sodium hydroxide solution to a phenolphthalein end point, what is the molarity of the acid?

• A. 0.020M
• B. 0.100M
• C. 0.025M
• D. 0.050M

Hint:

Always account for stoichiometric coefficients in acid–base titrations.

Answer 1

The Correct Option is C

Step 1: Moles of NaOH used: nNaOH = 0.025 × 0.050 = 0.00125mol Step 2: Reaction: H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O Step 3: Moles of H₂SO₄: nₐcid = (0.00125)/(2) = 0.000625mol Step 4: Molarity of acid: M = (0.000625)/(0.025) = 0.025M