What are Catalysts? (Edexcel IGCSE Chemistry (Modular))
Revision Note
The effect of a catalyst on rate of reaction
Catalysts are substances which speed up the rate of a reaction without themselves being altered or consumed in the reaction
Normally only small amounts of catalysts are needed to have an effect on a reaction
The mass of a catalyst at the beginning and end of a reaction is the same
Catalysts do not form part of the chemical equation but they are sometimes seen above or below the reaction arrow:
N2 (g) + 3H2 (g) 2NH3 (g)
SO2 (g) + O2 (g) SO3 (g)
Different processes require different types of catalysts but they all work on the same principle:
They provide an alternative pathway for the reaction to occur
The alternative pathway has a lower activation energy
Catalysts work by attracting reactant molecules on to the surface and so providing an alternate reaction pathway of lower energy
Catalysis is a very important branch of chemistry in commercial terms as catalysts increase the rate of reaction (hence the production rate) and they reduce energy costs
The transition metals are used widely as catalysts as they have variable oxidation states allowing them to readily donate and accept different numbers of electrons
This is key to their catalytic activity
Enzymes act as catalysts in biological systems
Examiner Tip
The effect of a catalyst on activation energy can be shown on a reaction profile.
Last updated:
You've read 0 of your 10 free revision notes
Unlock more, it's free!
Did this page help you?