Rates of Reaction
Factors affecting rate, collision theory, catalysts
Rates of Reaction
Reaction rate depends on: concentration (more particles, more collisions), temperature (faster particles, more energetic collisions), surface area (more exposed particles), and catalysts (lower activation energy). Collision theory explains these effects.
Example
Factors Affecting Rate
Concentration: zinc in concentrated HCl reacts faster than in dilute HCl. Temperature: milk spoils faster outside the fridge. Surface area: powdered zinc reacts faster than a strip. Catalyst: MnO2 speeds up H2O2 decomposition.
Note
Exam Tip
Use collision theory to explain each factor. A catalyst provides an alternative pathway with lower Ea — it is not consumed. Draw energy profiles showing the catalyst's effect.
Key Vocabulary
Reaction rateThe speed at which reactants are converted to products
CatalystA substance that increases reaction rate without being consumed
Collision theoryParticles must collide with sufficient energy and correct orientation to react
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Reaction rate
Speed: