In which of the following scenarios would you expect the rate of reaction to increase?
A) Decreasing the temperature
B) Increasing the concentration of reactants
C) Reducing surface area of a solid reactant
D) Diluting the reaction mixture
The correct answer and explanation is:
The correct answer is B) Increasing the concentration of reactants.
Explanation:
The rate of a chemical reaction is influenced by several factors, including temperature, concentration, surface area, and the presence of catalysts. Let’s go through each option:
- Decreasing the temperature (Option A): Lowering the temperature generally decreases the rate of reaction. This is because at lower temperatures, particles have less kinetic energy and move more slowly, leading to fewer collisions between reactant molecules. The energy of collisions is also lower, so it is less likely that the collisions will have enough energy to break bonds and initiate the reaction. Therefore, decreasing the temperature would slow down the reaction rate.
- Increasing the concentration of reactants (Option B): Increasing the concentration of reactants leads to an increase in the number of molecules or ions in the same volume. This means there are more frequent collisions between reactant molecules. As a result, the likelihood of successful collisions (those with sufficient energy to overcome the activation energy barrier) increases, thus speeding up the reaction. Higher concentration means a higher rate of reaction, provided that other factors remain constant.
- Reducing surface area of a solid reactant (Option C): Reducing the surface area of a solid reactant would decrease the rate of reaction. For a solid to react, its surface must come into contact with the other reactants. If the surface area is reduced (e.g., by breaking the solid into larger pieces), fewer reactant molecules can interact with the surface at any given time, leading to a decrease in the frequency of collisions and a slower reaction rate.
- Diluting the reaction mixture (Option D): Diluting the reaction mixture involves decreasing the concentration of reactants by adding solvent. This reduces the number of reactant molecules per unit volume, which in turn reduces the frequency of collisions between reactants, leading to a slower reaction rate.
In summary, increasing the concentration of reactants (Option B) results in more frequent and effective collisions, which increases the rate of reaction.