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Difficulty: MediumFactors Affecting Rates of Reaction

Match each change in reaction conditions to its corresponding effect on the kinetic model of reaction rates.

  • Increasing reactant concentration in solutionIncreases collision frequency by raising the number of solute particles per unit volume
  • Adding a positive catalystProvides an alternative reaction pathway with a lower activation energy (EaE_a)
  • Grinding a solid reactant into a fine powderExposes more reactant particles, increasing contact surface area for collisions per unit time
  • Increasing temperature of the reaction mixtureIncreases average kinetic energy, raising the proportion of collisions with energy E≥EaE \geq E_a

Answer

1. Increasing reactant concentration matches with increasing collision frequency by raising the number of solute particles per unit volume; 2. Adding a positive catalyst matches with providing an alternative pathway with lower activation energy; 3. Grinding solid reactant into fine powder matches with exposing more surface area for collisions; 4. Increasing temperature matches with raising average kinetic energy and the proportion of collisions with energy equal to or exceeding activation energy.
Each factor uniquely modifies a component of collision theory: concentration alters particle density and collision frequency; catalysts lower the activation energy threshold; surface area determines exposed reactive sites; temperature enhances molecular kinetic energy and the proportion of successful high-energy collisions.

Step-by-Step Solution

1
Evaluate the effect of concentration on particle distribution
More solute particles exist in a given volume when concentration increases.
Higher particle density directly increases collision frequency.
2
Evaluate the catalytic mechanism
A positive catalyst changes the reaction pathway.
This alternative pathway has a lower activation energy barrier (EaE_a).
3
Evaluate particle size reduction
Grinding a solid exposes interior atoms/molecules to the surrounding fluid.
Greater exposed surface area yields a higher number of effective collisions per unit time.
4
Evaluate kinetic energy distribution with temperature change
Higher temperature shifts the Maxwell-Boltzmann distribution curve to higher kinetic energies.
A significantly larger fraction of colliding species possess kinetic energy greater than or equal to EaE_a.

Key Concept

Collision theory explanations for factors influencing reaction rates
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Topics

Factors Affecting Rates of Reaction