Chemistry Reference
In-Depth Information
CO
2
H
2
O
N
2
a
Catalytic converter.
CO
HC
NO
x
b
A section through a catalytic converter.
Figure 7.15
noted, however, that the catalytic converter can
only be used with unleaded petrol and that, due
to impurities being deposited on the surface of the
catalyst, it becomes poisoned and has to be replaced
every fi ve or six years.
Questions
1
Using a catalysed reaction of your choice, devise an
experiment to follow the progress of the reaction and
determine how effective the catalyst is.
2
Why do some people consider catalytic converters not
to be as environmentally friendly as suggested in their
advertising material?
3
Unreacted hydrocarbons such as octane, C
8
H
18
(from
petrol), also form part of the exhaust gases. These gases
are oxidised in the converter to carbon dioxide and water
vapour. Write an equation for the oxidation of octane.
Figure 7.16
The haze is due to pollution caused mainly by cars without
catalyst exhaust systems.
●
Enzymes
Enzymes
are protein molecules produced in living
cells. They are catalysts which speed up hundreds of
different chemical reactions going on inside living
cells. These biological catalysts are very specifi c in
that each chemical reaction has a different enzyme
catalyst. There are literally hundreds of different
kinds of enzyme. Enzymes all have an active site.
The active site is a particular shape and locks into a
corresponding shape in a reactant molecule. When
this has happened, the enzyme can work to break up
the reactant (Figure 7.17).
