Stoichiometric calculation from titration volumes and reaction ratio

Steps:

• Moles of NaOH = 0.100 mol dm⁻³ × (25.0 / 1000) dm³ = 0.0025 mol.
• From 2:1 ratio (2NaOH : 1H₂SO₄), moles of H₂SO₄ = 0.0025 / 2 = 0.00125 mol.
• Volume of H₂SO₄ = 20.0 / 1000 = 0.020 dm³.
• Concentration of H₂SO₄ = 0.00125 mol / 0.020 dm³ = 0.0625 mol dm⁻³.

Why A is correct:

• Balanced equation dictates 2:1 mole ratio, ensuring accurate stoichiometric equivalence in titration.

Why the others are wrong:

• B assumes 1:1 mole ratio, ignoring sulfuric acid's two H⁺ ions.
• C doubles NaOH moles without adjusting for acid volume.
• D inverts ratio, treating 1:2 instead of 2:1.

Final answer: A