Rates of Reaction Factors (CIE IGCSE Chemistry)

There are several factors that can affect the rate of a reaction. These are:

• • Concentration of the reactants in solution or the pressure of reacting gases
  • Temperature at which the reaction is carried out
  • Surface area of solid reactants
  • The use of a catalyst
• Changes in these factors directly influence the rate of a reaction
• It is of economic interest to have a higher rate of reaction as this implies a higher rate of production and hence a more efficient and sustainable process

The effect of increased concentration or pressure

Explanation:

• Compared to a reaction with a reactant at a low concentration, the graph line for the same reaction but at a higher concentration/pressure has a steeper gradient at the start and becomes horizontal sooner
• This shows that with increased concentration of a solution or increased pressure of a gas, the rate of reaction will increase 

The effect of surface area 

Graph showing the effect of increased surface area on the rate of reaction

Explanation:

• Compared to a reaction with lumps of reactant, the graph line for the same reaction but with powdered reactant has a steeper gradient at the start and becomes horizontal sooner
• This shows that with increased surface area of the solid, the rate of reaction will increase

The effect of temperature 

Graph showing the effect of temperature on the rate of reaction

Explanation:

• Compared to a reaction at a low temperature, the graph line for the same reaction but at a higher temperature has a steeper gradient at the start and becomes horizontal sooner
• This shows that with increased temperature, the rate of reaction will increase

The effect of using a catalyst

• Catalysts are substances which speed up the rate of a reaction without themselves being altered or consumed in the reaction
• The mass of a catalyst at the beginning and end of a reaction is the same and they do not form part of the equation

Graph showing the effect of using a catalyst on the rate of reaction

Explanation:

• Compared to a reaction without a catalyst, the graph line for the same reaction but with a catalyst has a steeper gradient at the start and becomes horizontal sooner
• This shows that with a catalyst, the rate of reaction will increase