Reaction Kinetics — Flashcards & Quiz

Key Points

• Collision theory: reactants must collide with sufficient energy (≥ activation energy Eₐ) AND correct orientation to react.
• Activation energy (Eₐ): the minimum energy required for a successful reaction; varies by reaction.
• Factors increasing reaction rate: higher concentration (more collisions), higher temperature (more energy AND more collisions), larger surface area (for solids), catalyst (lowers Eₐ).
• Catalysts provide an alternative reaction pathway with lower Eₐ. They are not consumed in the reaction.
• Maxwell-Boltzmann distribution: shows the distribution of kinetic energies in a gas. Higher T shifts the curve right and flattens it; more molecules have E ≥ Eₐ.
• Energy profile diagram: shows reactants, transition state (top of the hump), and products; the hump height is Eₐ, the difference between reactants and products is ΔH.

Common Mistakes to Avoid

1. Claiming catalysts change the equilibrium position — they don't, they only speed up attainment.
2. Saying temperature only matters for the rate of successful collisions — higher T also means more collisions per second.
3. Drawing Maxwell-Boltzmann distributions without shifting AND flattening at higher T.
4. Confusing activation energy (reaction rate) with enthalpy change (exo/endothermic).
5. Forgetting to include the transition state in energy profile diagrams.

Exam Strategy

BSSS Unit 2 kinetics questions ask you to explain rate changes using collision theory. Method: (1) identify the factor being changed (concentration, T, surface area, catalyst), (2) explain in terms of collisions (frequency and energy), (3) support with a Maxwell-Boltzmann diagram if relevant, (4) distinguish effects on rate from effects on equilibrium position.

Revision Tip

Collision theory is a reusable framework — drill a Revizi deck that gives you a rate-change scenario and asks you to explain using collision frequency and energy.