Kinetics and Rate Equations
Collision theory, activation energy, Maxwell-Boltzmann distributions, catalysts, experimental rate measurement, orders, rate constants and mechanisms.
How to study A-level Chemistry
Represent the species and process correctly, conserve atoms, charge and energy, calculate with units, then test the result against observations and chemical evidence.
Core concepts
Concept 1
Reaction rate depends on collision frequency, orientation and the fraction of collisions exceeding activation energy.
Exam cue: Use concentration ratios and rate ratios to infer each order.
Concept 2
Temperature changes the energy distribution; catalysts provide an alternative route with lower activation energy.
Exam cue: Include units for the rate constant derived from the overall order.
Concept 3
Experimental data determine rate equation, order and rate constant and can constrain a rate-determining step.
Exam cue: Relate a proposed mechanism to the observed rate equation rather than treating it as direct observation.
Risk pitfalls and guardrails
Saying a catalyst changes equilibrium yield.
Guardrail: Do not substitute a memorised equation, mechanism or trend until you have identified the species, conditions and chemical model required.
Assuming equation coefficients are reaction orders.
Guardrail: Do not substitute a memorised equation, mechanism or trend until you have identified the species, conditions and chemical model required.
Describing temperature only as causing more collisions without the activation-energy fraction.
Guardrail: Do not substitute a memorised equation, mechanism or trend until you have identified the species, conditions and chemical model required.
Memory anchors
Rate
Rate is change in concentration of a reactant or product per unit time.
Activation Energy
Activation energy is the minimum energy required for a successful reaction pathway.
Catalyst
A catalyst increases rate by an alternative pathway and is regenerated overall.
Order of Reaction
Order is the power of a concentration term in the experimentally determined rate equation.
Rate Constant
The rate constant links rate to concentrations at a stated temperature.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
What is the instantaneous rate at a point on a concentration–time graph?
Product amount rises from 0.0120 to 0.0300 mol in 45.0 s. What is the mean formation rate?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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