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Difficulty: MediumRate of Reaction and Collision Theory

According to collision theory, which of the following best explains why adding a positive catalyst increases the rate of a chemical reaction?

  1. It provides an alternative reaction pathway with a lower activation energy, increasing the proportion of effective collisions.Answer
  2. B
    It shifts the position of dynamic equilibrium to favor the formation of products.
  3. C
    It increases the average kinetic energy of the reacting particles in the system.
  4. D
    It increases the total enthalpy change (ΔH\Delta H) of the overall reaction.

Answer

A catalyst increases the reaction rate by providing an alternative pathway with a lower activation energy, thereby increasing the fraction of colliding particles with energy E≥EaE \ge E_a.
The correct option explains that a positive catalyst lowers the activation energy (EaE_a) by providing an alternative mechanism. Consequently, a greater percentage of molecular collisions possess the requisite energy to overcome the energy barrier, resulting in a higher rate of effective collisions.

Step-by-Step Solution

1
Define collision theory criteria for effective collisions
For a collision to result in a chemical reaction, colliding particles must possess minimum activation energy (EaE_a) and correct molecular orientation.
Establishing the essential requirements for a successful chemical transformation.
2
Analyze the action of a positive catalyst
A positive catalyst offers an alternative reaction mechanism featuring an activated complex of lower energy.
Determining how the energy barrier is modified in the presence of a catalyst.
3
Evaluate the effect on reaction rate and equilibrium
Lowering EaE_a means a higher fraction of reactant particles have kinetic energy E≥EaE \ge E_a, increasing collision frequency successfully without shifting equilibrium or changing overall ΔH\Delta H.
Connecting activation energy reduction directly to rate increase.

Key Concept

Role of Catalysts in Collision Theory
Estimated Time:1m 0s
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Topics

Rate of Reaction and Collision Theory