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Factors affecting rate of reaction

 

Changes in matter ] Importance of chemical reactions ] Chemical Reactions ] On-line practice ]

Rates of reaction are affected by :

  • Temperature
    • Raising the temperature makes the particles move faster. This means that the particles collide more frequently with each other and the rate of the reaction increases.

    • Also, the faster the particles are traveling, the greater is the proportion of them which will have the required activation energy for the reaction to occur.

          

       

  • Concentration
    • Increasing the concentration of a substance in solution means that there will be more particles per dm3  of that substance.

    • The more particles that there are in the same volume, the closer to each other the particles will be. This means that the particles collide more frequently with each other and the rate of the reaction increases.

  • Pressure
    • Increasing the pressure of a reaction where the reactant is a gas is similar to increasing the concentration of a reactant in a solution.

    • The gas particles (usually molecules) will be closer together when the pressure increases. This means that the particles collide more frequently with each other and the rate of the reaction increases.

     

  • Surface area
    • A solid in a solution can only react when particles collide with the surface.

    • The bigger the area of the solid surface, the more particles can collide with it per second, and the faster the reaction rate is.

    • You can increase the surface area of a solid by breaking it up into smaller pieces. A powder has the largest surface area and will have the fastest reaction rate.


  • Catalyst
    • A catalyst will change the rate of a reaction. A catalyst is often used to make a reaction go faster.

    • The catalyst itself does not take part in the reaction as a reactant. It is not changed by the reaction, it is not used up during the reaction. It is still there in the same form when the reaction is complete.

    • A catalyst works by providing a convenient surface for the reaction to occur.

    • The reacting particles gather on the catalyst surface and

      • collide more frequently with each other

      • more of the collisions result in a reaction between particles because the catalyst can lower the activation energy for the reaction.

    • A catalyst is often used as a powder, so that it has a bigger surface area per gram.

       

Exothermic and endothermic changes ] Energy level diagrams ] Activation energy ] Rates of reaction ] [ Factors affecting rate of reaction ]