EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 复习笔记:3.2.3 Catalysts

EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 复习笔记:3.2.3 Catalysts

Catalysts & Rates

 

  • Catalysts are substances which speed up the rate of a reaction without themselves being altered or consumed in the reaction
  • The mass of a catalyst at the beginning and end of a reaction is the same and they do not form part of the equation
  • An important industrial example is iron, which is used to catalyse the Haber Process for the production of ammonia
  • Iron beads are used to increase the surface area available for catalysis
  • Normally only small amounts of catalysts are needed to have an effect on a reaction
  • Different processes require different types of catalysts but they all work on the same principle of providing an alternate route for the reaction to occur
  • They do this by lowering the activation energy required, hence providing a reaction pathway requiring less 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

 

5.6-Reaction-Kinetics-Iron-Catalyst-15.6-Reaction-Kinetics-Iron-Catalyst-2

 

Catalysts work by attracting reactant molecules on to the surface and so providing an alternate reaction pathway of lower energy

 

 

Exam Tip

Although catalysts are not part of the overall reaction, you may see them written over the arrow in reaction equations in the same way you can add reaction conditions above or below the arrow.

转载自savemyexams

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