Surface Area's Role in Reaction Rates

Steps:

• Conclusion 1 states powdered calcium carbonate reacts faster with HCl than large pieces, which aligns with increased exposure for collisions.
• Conclusion 2 states grinding increases surface area, a direct physical effect of particle size reduction.
• Increased surface area from powdering allows more reactant molecules to collide with the solid, explaining the faster rate in conclusion 1.
• Both conclusions are factually correct, with 2 providing the mechanistic explanation for 1.

Why A is correct:

• Per collision theory, reaction rate in heterogeneous reactions increases with surface area, as more sites enable frequent effective collisions.

Why the others are wrong:

• B: Incorrect, as increased surface area directly causes the faster reaction rate.
• C: Incorrect, as grinding objectively increases surface area by exposing more material.
• D: Incorrect, as powdered form reacts faster due to greater surface exposure.

Final answer: A