How does increasing surface area affect the reaction rate?

How does increasing surface area affect the reaction rate?

• A. Slower
• B. Faster
• C. No effect
• D. Requires less energy

Answer: (B)

Increasing surface area increases the rate of a reaction because more surface sites are available for reactant molecules to collide with. When a solid reactant is exposed to a liquid or gas, the rate at which products form depends on how often reactive encounters occur at those surfaces. Grinding a solid into smaller pieces or turning it into a powder dramatically raises the surface area, giving many more points for collisions per unit time. Since the rate in such cases is largely controlled by how often collisions happen (the collision frequency at the surface), more surface area means more successful collisions and a faster reaction. The activation energy for each collision doesn’t change with surface area, so the energy barrier isn’t reduced; there are just more chances per unit time to overcome it. In a purely homogeneous solution reaction, surface area isn’t typically a factor, but for reactions involving a solid surface, increasing surface area speeds things up.

Increasing surface area increases the rate of a reaction because more surface sites are available for reactant molecules to collide with. When a solid reactant is exposed to a liquid or gas, the rate at which products form depends on how often reactive encounters occur at those surfaces. Grinding a solid into smaller pieces or turning it into a powder dramatically raises the surface area, giving many more points for collisions per unit time. Since the rate in such cases is largely controlled by how often collisions happen (the collision frequency at the surface), more surface area means more successful collisions and a faster reaction. The activation energy for each collision doesn’t change with surface area, so the energy barrier isn’t reduced; there are just more chances per unit time to overcome it. In a purely homogeneous solution reaction, surface area isn’t typically a factor, but for reactions involving a solid surface, increasing surface area speeds things up.