ACKNOWLEDGEMENT:
Figure
|
Source of Figure
|
Figure 4
|
http://www.chemguide.co.uk
|
Figure 5
|
http://www.chemguide.co.uk
|
Particle size of the reactants:
The particle size of
the reactants has a great effect on the rate of reactions. The smaller the
particle of the reactants, the faster the rate of the reaction, and vice versa.
Explanation:
The smaller the
particle, the smaller is its surface area to volume ratio. Therefore, it is
easier for the particle to react from all sides.
Figure 4:
Examples:
i.
Powdered
sugar dissolves more quickly and easily than lumps of sugar.
ii.
It
is easier to peel bigger potatoes than smaller ones.
Mathematical Explanation:
Parameters
|
Cube
1 – (1cm)
|
Cube
2 – (2cm)
|
Cube
3 – (3cm)
|
|||
 |
 |
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Surface
Area
|
1cm2 x 6 = 6cm2
|
2cm2 x 6 = 24cm2
|
9cm2 x 6 = 54cm2
|
|||
Volume
|
1cm3
|
8cm3
|
27cm3
|
|||
Surface
Area : Volume
|
6/cm
|
3/cm
|
2/cm
|
Presence of a catalyst:
Catalyst:
Catalysts are
substances (elements, mixtures or compounds) that speed up the rate of
reactions without themselves being chemically participating in the reaction. It
may physically change its form, for example it may begin as lumps and become
powder by the end of the reaction.
How do catalysts speed up the rate of reaction?
Catalysts speed up the
rate of reaction by lowering the activation energy of the reaction, or
providing an alternate, “lower” activation energy route to form products.
Figure 5:
Enzymes:
Enzymes are biological
catalysts which speed up the rate of biological reactions in living beings.
Example: Digestion of
food.
Commonly used catalysts:
Transition metals have
catalytic properties. Table 2 shows some Transition metals being used as
catalyst in important industrial processes.
Table 2:
Name
of the Process
|
Detail
of the Process
|
Catalyst
used
|
Harber Process
|
Industrial manufacture of Ammonia (NH3)
|
Iron
|
Contact Process
|
Industrial manufacture of Sulphuric
Acid (H2SO4)
|
Vanadium(V)Oxide
|
Hydrogenation of Alkenes
|
Conversion of Alkenes to Alkanes
|
Nickle
|
Hydrogenation of Unsaturated Fats
|
Manufacture of Margarine
|
Nickle
|
