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Catalysts

A catalyst increases the rate of a reaction by providing an alternative reaction pathway with a lower activation energy.In a reversible reaction, a catalyst speeds up the forward and reverse reactions by the same factor. This means it has no effect on the position of equilibrium or the value of Kc.A catalyst increases the rate at which equilibrium is reached, so the same equilibrium mixture is produced in less time.In industry this is very useful. For example, iron is used in the Haber process so that a reasonable yield of ammonia is made quickly at a temperature that is not too high, saving energy and money.

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Specification: AQA Chemistry (7404), AS-level, 3.1.6.1 Chemical equilibria and Le Chatelier's principle. Topic: Equilibria.

Key terms in this lesson

Catalyst
A substance that increases the rate of a chemical reaction without being used up, by providing an alternative reaction pathway with a lower activation energy.
Equilibrium constant
A value, Kc, that expresses the relative concentrations of products and reactants at equilibrium for a reaction.
Position of equilibrium
The relative amounts of reactants and products present when a reversible reaction has reached equilibrium.
Oxidation
The addition of oxygen, the removal of hydrogen, the loss of electrons, or an increase in oxidation number.
Reduction
The removal of oxygen, the addition of hydrogen, the gain of electrons, or a decrease in oxidation number.

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