Chemistry Paper 2 – The Rate of Reaction & Catalysts

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. 

Catalysts 

Catalysts increase the rate of chemical reactions…