If 5.0 g of marble reacts with 25.0 cm3 hydrochloric acid; which of the following combinations has the fastest reaction rate?

A. Marble chips and 2.0 mol dm−3 HCl(aq)
B. Marble chips and 2.5 mol dm−3 HCl(aq)
C. Powdered marble and 2.5 mol dm−3 HCl(aq)
D. Powdered marble and 2.0 mol dm−3 HCl(aq)

Correct Answer:

Option C – Powdered marble and 2.5 mol dm−3 HCl(aq)

Explanation

Powdered marble reacts more rapidly with HCl than the chips of marble because:
Surface area of powdered marble is more that of chips of marble and hence there is more collisions between the molecules of reactants
Number of molecules increases.
Energy of activation decreases
Marble chips will not react with HCl