Inorganic and Applied Chemistry

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Inorganic and Applied Chemistry

3.4 Chemical kinetics and catalysts

After the introduction of rate of reaction we have seen how a chemical reaction depends of other things than

stoichiometry. It is thereby reasonable to assume that the temperature also plays a significant role for the

cause and velocity of reaction. This combination is described by the Arrhenius-equation named after the

Swedish chemist Svante Arrhenius due to his work on reaction kinetics in the 1880 ́ies. The Arrhenius-

equation gives the connection between temperature, reaction constant and the concentration of reactant in the

following manner:

ln( )^1 ln(A)

R T

E

k a  (3- 3)

in which R is a universal constant called the gas constant and T is the temperature in Kelvin (absolute

temperature). The parameter Ea is called the energy of activation. One can imagine that if a reaction should

take place the reactants must collide and become products. This requires a certain amount of energy as there

is a barrier to be overcome if the reactants should become products. The parameter Ea may be seen as the

magnitude of this barrier. Does Ea have a large value it is difficult to make the products whereas it is easy to

obtain the products if Ea has a small value. In the following example we shall look at a case where a value of

Ea can be calculated using the Arrhenius-equation.

Reactions kinetics

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