Factors Affecting Rate of Reaction
Chemistry: Cambridge International GCSE Supplement, topic 6.2.2
Rate of Reaction - Key Factors
The main factors that affect the rate of chemical reactions are:
Concentration of dissolved reactants
- Increasing the concentration increases the frequency (number) of collisions. This increases the rate of reaction.
Pressure of gas reactants
- Increasing pressure is like increasing the concentration.
- It increases the frequency (number) of collisions. This increases the rate of reaction (makes the reaction faster).
Temperature
- Increasing the temperature increases the frequency (number) of collisions.
- Increasing the temperature increases the energy of reactant particles. This means that a greater proportion (more) of the particles will have more energy than the activation energy that is needed.
- Together, these lead to more successful collisions. This increases the rate of reaction.
Surface area of solid reactants
- Increasing the surface area increases the frequency (number) of collisions. This increases the rate of reaction.
- This is often done by breaking up solids into smaller lumps (e.g. powders).
- This increase in surface area to volume ratio makes sure that more particles are exposed to attack.
Catalysts
- Catalysts are substances that increase the rate of a chemical reaction without being used up in the process.
Test yourself on Factors Affecting Rate of Reaction
Limestone and marble structures crumble when reacted with acid. How will the recent increase in concentration of acid in rainwater affect the rate at which limestone and marble are being worn away?