Reaction rate and mass loss differences between carbonate and metal with acid

Steps:

• Identify reactions: CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂ (exp 1); Mg + 2HCl → MgCl₂ + H₂ (exp 2).
• Calculate mass loss: 5g CaCO₃ (0.05 mol) produces 0.05 mol CO₂ (2.2g loss); 5g Mg (0.208 mol) produces 0.104 mol H₂ (0.208g loss).
• Compare rates: Carbonate-acid reaction is faster (rapid effervescence) than Mg-acid (slower initial rate with 1 mol/dm³ HCl).
• Predict graphs: Exp 1 shows steeper initial slope and larger total drop; exp 2 shows shallower slope and smaller drop.

Why C is correct:

• Matches stoichiometry: Larger CO₂ mass loss (from formula CaCO₃ + 2HCl → CO₂) versus smaller H₂ loss (Mg + 2HCl → H₂), with faster CaCO₃ rate per collision theory.

Why the others are wrong:

• A: Reverses rates, showing slower CaCO₃ drop.
• B: Equal mass losses, ignoring molar mass differences.
• D: Similar slopes, overlooking reaction speed variance.

Final answer: C