Catalysts (Oxford AQA International A Level Chemistry)
Revision Note
Written by: Philippa Platt
Reviewed by: Stewart Hird
Catalysts & Rate of Reaction
Catalysis is the process in which the rate of a chemical reaction is increased, by adding a catalyst
A catalyst increases the rate of a reaction by providing the reactants with an alternative reaction pathway which is lower in activation energy than the uncatalysed reaction
Catalysts can be divided into two types:
Homogeneous
Heterogeneous
Homogeneous means that the catalyst is in the same phase as the reactants, for example
Concentrated sulfuric acid in esterification
Heterogeneous means that the catalyst is in a different phase to the reactants, for example
Aluminium oxide in cracking hydrocarbon chains from crude oil
Iron in the Haber process (production of ammonia)
Catalytic convertors in cars exhausts
Maxwell-Boltzmann distribution curve
Catalysts provide the reactants another pathway which has a lower activation energy
By lowering Ea, a greater proportion of molecules in the reaction mixture have the activation energy, and therefore have sufficient energy for an effective collision
As a result of this, the rate of the catalysed reaction is increased compared to the uncatalyzed reaction
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