Which of the following factors generally increases the rate of a chemical reaction?
I. Decrease in temperature
II. Increase in concentration of reactants
III. Addition of a catalyst
IV. Decrease in surface area of solid reactants
Correct: B
Let's analyze each factor:
I. Decrease in temperature: Lowers the kinetic energy of particles, reducing the frequency and energy of collisions, thus decreasing the reaction rate.
II. Increase in concentration of reactants: Leads to more particles per unit volume, increasing the frequency of effective collisions, and thus increasing the reaction rate.
III. Addition of a catalyst: Provides an alternative reaction pathway with a lower activation energy, speeding up the reaction without being consumed.
IV. Decrease in surface area of solid reactants: Reduces the exposed area for reaction, leading to fewer collisions and a slower reaction rate.
Therefore, increasing the concentration of reactants and adding a catalyst generally increase the rate of a chemical reaction.