Magnesium is limiting reactant; same total H₂ but different rates due to acid concentration

Steps:

• Moles of Mg = 2.0 g / 24 g/mol = 0.083 mol in both experiments.
• Moles of H₂SO₄ in Experiment 1 = 0.100 dm³ × 1.0 mol/dm³ = 0.100 mol.
• Moles of H₂SO₄ in Experiment 2 = 0.050 dm³ × 2.0 mol/dm³ = 0.100 mol.
• Reaction stoichiometry (1:1 Mg:H₂SO₄) shows Mg limits reaction; both yield 0.083 mol H₂ (same volume at 25°C), but Experiment 2's higher [H₂SO₄] gives faster initial rate.

Why A is correct:

• Graph A depicts both curves reaching identical maximum H₂ volume with Experiment 2 steeper initially, matching limiting reactant and rate law (rate ∝ [H₂SO₄]).

Why the others are wrong:

• B shows unequal maximum volumes, contradicting equal moles of limiting Mg.
• C shows identical rates, ignoring higher [H₂SO₄] in Experiment 2.
• D shows Experiment 1 faster, reversing concentration-rate relationship.

Final answer: A