How does concentration affect rate?

• A. Higher concentration increases temperature
• B. Higher concentration changes the activation energy
• C. Higher concentration has no effect
• D. Higher concentration leads to more frequent collisions

Answer: (D)

The rate of a reaction is tied to how often reacting particles collide. When you raise the concentration, you pack more particles into the same volume, so collisions happen more frequently. More collisions per unit time means more opportunities for reactants to meet with the right orientation and enough energy to overcome the activation barrier, so the overall rate increases. The activation energy itself is a fixed barrier for the reaction and isn’t altered just by changing concentration, and temperature changes would affect both collision energy and the fraction of successful collisions—not concentration alone. Thus, higher concentration speeds things up by boosting collision frequency, not by changing the energy barrier.