Same hydrogen volume, different reaction rates due to acid concentration

Steps:

• Moles of Mg = 2.0 g / 24 g/mol = 0.083 mol (limiting reactant, produces 0.083 mol H₂).
• Exp 1 acid: 0.100 dm³ × 1.0 mol/dm³ = 0.10 mol H₂SO₄ (excess).
• Exp 2 acid: 0.050 dm³ × 2.0 mol/dm³ = 0.10 mol H₂SO₄ (excess, same total but higher concentration).
• Rate ∝ [H₂SO₄], so Exp 2 faster; both reach same final H₂ volume.

Why A is correct:

• Matches rate law (reaction rate proportional to acid concentration) with identical final volumes and steeper curve for Exp 2.

Why the others are wrong:

• B: Incorrect final volumes differ, violating equal excess acid.
• C: Identical curves ignore concentration's rate effect.
• D: Reverses rates, contradicting higher [H₂SO₄] speeds reaction.

Final answer: A