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What is a Catalyst?
· A substance that increases the rate of a chemical
reaction without itself undergoing any permanent
chemical change.
· The process of speeding up a chemical reaction
using a catalyst is known as catalysis.
· Biological catalysts are called enzymes.…read more

Slide 3

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General characteristics of
· A catalyst remains unchanged in mass and chemical
composition at the end reaction. However there may
be a physical change.
· Catalysts alter the rate of chemical reaction.
· They are specific.
· Only small quantity is need for a reaction.
· Catalysts does not affect the amount of product
formed, only the rate at which it is formed.
· Catalysts lower activation energy by providing a
different mechanism through which the reaction can
go.…read more

Slide 4

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How do Catalysts work?
Catalysts speed up reactions by providing an alternate reaction
pathway for the breaking and remaking of bonds that has a
lower activation enthalpy.…read more

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Types of Catalysts
Homogenous Catalysts
· Reactants & catalysts in the same physical state
· Example: enzymatic reactions in cells (occur in aq.
Heterogeneous Catalysts
· Reactants & catalysts in different physical state
· Example: Many industrial processes like
hydrogenation of an unsaturated organic compound…read more

Slide 6

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Mechanism of Heterogeneous
· Reactants get adsorbed onto catalyst
· Bonds in the reactant get weakened
and they break.
· New bonds form between the
reactants, held close together on the
surface, to form products.
· This in turn weakens the bonds to the
catalyst surface and the product
molecules are released.
· Leaves the catalyst free for a new
reaction.…read more

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