Titration stoichiometry for acid-base reaction

Steps:

• Calculate moles of NaOH: (25.0/1000) dm³ × 0.100 mol dm⁻³ = 0.0025 mol.
• From balanced equation, 2 mol NaOH reacts with 1 mol H₂SO₄, so moles 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:

• It equals the concentration from moles of acid divided by volume, using the 1:2 mole ratio in the equation.

Why the others are wrong:

• B assumes half the correct acid moles, ignoring full stoichiometry.
• C treats reaction as 1:1 NaOH:H₂SO₄, overestimating acid concentration.
• D doubles the 1:1 calculation, further inflating the value.

Final answer: A