Chapter 8 Unit 2 AQA AS Chemistry

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  • Created by: Rachel
  • Created on: 16-04-11 21:20

Collision Theory

Particles must collide with enough energy to break the bonds in order to react.

To increase the rate of reaction: increase temperature, increase concentration, increase pressure (gas only), increase surface area (solid only), use of a catalyst

Minimum energy required to start a reaction = activation energy, E

( complex = transition state

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Maxwell-Boltzmann Distribution


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Provide a different reaction pathway with a lower activation energy.


Haber process = iron

Otswald process for making nitric acid = platinum/rhodium

Hardening of fats with hydrogen = nickel

Heterogeneous: where the catalyst is in different phase to the reactants, usually a solid catalyst and liquid or gaseous reactants.

Homogeneous: where the catalyst and reactants are in the same phase

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Catalytic Converters

Reduce levels of pollutants

Honeycomb of ceramic coated with platinum and rhodium

Shape = large surface area so a little expensive metal goes a long way

Gases pass over catalyst and react to form less harmful products

carbon monoxide + nitrogen oxides  ---> nitrogen + carbon dioxide

hydrocarbons + nitrogen oxides ---> nitrogen + carbon dioxide + water

1. Gases form weak bonds with the metal atoms of the catalyst (adsorption) which holds the gases in the right position to react together. They react on the surface.

2. The products then break away from the metal atoms (desorption) which frees up room for more gases to react.

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