3.2 Catalysts At Work
1. Catalytic Converters
LO: I understand how the catalytic converter in a car
exhaust system converts polluting gases into non-polluting
substances.
Modern car exhaust systems are fitted with
to get rid of polluting gases.
Platinum,
and
are used to
catalyse the following reactions within the exhaust:
Stage 1
2NO + 2NO2
Stage 2
2CO + O2
The molecules collide with the surface of the catalyst
and
to it.
This is called
The molecules form weak
.
with the catalyst.
This in turn
the bonds between the atoms in
the molecule so that they are more able to react with
each other.
After the reaction, the bonds between the catalyst and
the new molecules break, leaving the surface of the
catalyst ready to
more polluting molecules.
petrol must be used with catalytic converters.
Lead atoms in leaded petrol
to the surface of
the catalyst stopping the molecules of polluting gas from
adsorbing.
This is known as
the catalyst.
2. Heterogeneous Catalysis
LO: I know some examples of heterogeneous catalysis.
In heterogeneous catalysis the catalyst is in a different
state from the reactants.
In some reactions the catalyst can become
with by-products.
.
If the catalyst is expensive then it must be removed and
(renewed).
3. Homogeneous Catalysis
LO: I know some examples of homogeneous catalysis.
In homogeneous catalysis the catalyst is in the same
state as the reactants.
Enzymes are
catalysts. They are complex
protein molecules which speed up specific chemical
changes by homogeneous catalysis.