Question 1
Explain briefly how the surface area of the reactants changes the rate of reaction.
The right answer is the one marked above.
The powder has the greater surface area, so the number of collisions in unit time is greater. A solid only reacts at its surface, so more surface means more particles able to react at once.
The masses are equal — only the shape differs. Grinding does not turn the substance into a different chemical either; CaCO3 is still CaCO3.