Factors Influencing Reaction Rate in Mg + HCl

Steps:

• Reaction rate increases with HCl concentration due to more frequent collisions.
• Smaller magnesium pieces increase surface area, raising collision frequency and rate for graph 1.
• Fewer magnesium pieces (same mass) mean larger pieces, reducing surface area and slowing rate for graph 1.
• All three factors alter either concentration or surface area, explaining differences between graphs.

Why A is correct:

• Collision theory states reaction rate depends on reactant concentration and effective collisions, which surface area affects; all statements modify these.

Why the others are wrong:

• B omits statement 3, which reduces surface area and can slow the reaction.
• C omits statement 2, which increases surface area and can speed up the reaction.
• D omits statement 1, ignoring concentration's direct impact on collision rate.

Final answer: A