Rate of a Reaction | Chemistry for Grade 11 (IGCSE) PDF Download

Rates of Reaction Factors

• There are various factors that can influence how quickly a reaction occurs. 
• These include:
  • Concentration of the reactants: The amount of reactants in a solution or the pressure of gases involved.
  • Temperature: The level of heat at which the reaction takes place. Higher temperatures usually lead to faster reactions.
  • Surface area of solid reactants: The exposed area of solid substances that can react.
  • Use of a catalyst: A substance that can speed up a reaction without being used up itself.
• Changes in these variables directly impact the speed of a reaction. 
• It is important in terms of cost-effectiveness to have a faster reaction rate, as it implies increased production efficiency and sustainability.

The effect of increased concentration or pressure

Explanation:

• When a solution or gas has a higher concentration/pressure, the rate of reaction increases.
• This is evident from the steeper gradient and quicker horizontal level in reaction graphs.

The effect of surface area 

Explanation:

• Increasing the surface area of a solid in a reaction boosts the reaction rate.
• This is depicted by faster reaction completion shown in graphs with powdered reactants.

The Effect of Temperature

Explanation:

• When comparing a reaction at low temperature to the same reaction at a higher temperature, the graph line demonstrates a steeper initial gradient and reaches a horizontal plateau sooner.
• This illustrates that as temperature rises, the reaction rate accelerates.

The Effect of Catalysts on Rate of Reaction

• Catalysts are agents that enhance reaction rates without undergoing alteration or consumption themselves.
• The catalyst's mass remains unchanged from the beginning to the end of the reaction, and it does not factor into the reaction 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.