Particle size and reactant quantity affect reaction rate

Steps:

• Powdered calcium carbonate (experiment 1) has highest surface area, yielding fastest reaction rate with excess acid.
• Lumps (experiment 2) reduce surface area, slowing the rate but allowing completion with excess acid.
• Insufficient acid in lumps (experiment 3) limits reaction extent, causing early plateau.
• Curves typically show X as steepest/full, Y moderate/full, Z shallow/plateaued.

Why C is correct:

• Experiment 3 matches curve Z per rate laws: limited reactant halts reaction before completion (Le Chatelier's principle on equilibrium shift).

Why the others are wrong:

• A: Experiment 1 aligns with fastest curve (likely X), not specified as wrong but inconsistent if X is slowest.
• B: Experiment 2 fits moderate curve (likely Y), but question confirms mismatch.
• D: Identical to C, but listed separately—possibly a duplicate error.

Final answer: C