The branch of the physical chemistry which deals with the rate at which the chemical reactions occurs, the mechanism by which the chemical reaction occurs and the effect of various factors like pressure, concentration, temperature on the reaction rates is called the chemical kinematics.
Effects of temperature on the Rate of Reaction:
ØThe rate of a chemical reaction increases with increasing the temperature.
Effects of temperature on the Rate of Reaction:
ØThe rate of a chemical reaction increases with increasing the temperature.
ØA collision between reactant molecules must occur with a minimum
energy before effective yielding product molecules. This is called the activation energy. \(\left( {{E}_{a}} \right)\).
Ø The temperature coefficient of a chemical reaction is defined
as the ratio of the specific reaction
rates of a reaction at two temperatures differing by \({{10}^{0}}C\)\[\mu
=\frac{{{k}_{t}}+10}{{{k}_{t}}}\]\[\frac{{{k}_{{{T}_{2}}}}}{{{k}_{{{T}_{1}}}}}={{\mu}^{\frac{\left( {{T}_{2}}-{{T}_{1}} \right)}{10}}}={{\mu }^{\frac{\Delta T}{10}}}\]\[\log \left[ \frac{{{k}_{{{T}_{1}}}}}{{{k}_{T{{}_{2}}}}} \right]=\frac{\Delta
T}{10}\log \mu \]
Ø The larger the value of \({{E}_{a}}\), the smaller the value of rate
constant.
Ø At lower temperatures, an increase in temperature causes more than a
change in the value of k than that at higher
temperatures.
Arrhenius
equation:
A variation of the rate constant
k with temperature \(T\left( k \right)\)
is given by Arrhenius equation.
\[k=A.{{e}^{-\frac{Ea}{RT}}}\]\[\ln
k=\ln A-\frac{Ea}{RT}\]
\[\log
k=\log A-\frac{Ea}{2.303R}\]
A is called the
frequency factor.
\(A\And Ea\) are called as Arrhenius parameters.
\(A\And Ea\) are called as Arrhenius parameters.
If we plot a
graph between \[\log k\] and \[\frac{1}{T}\] , we get a straight line with
\[slope=-\frac{{{E}_{a}}}{2.303R}\]
\[Ea=2.303\times
R\times slope\]
\[\log
\frac{{{k}_{2}}}{{{k}_{1}}}=\frac{{{E}_{a}}}{2.303R}\left[
\frac{{{T}_{2}}-{{T}_{1}}}{{{T}_{1}}{{T}_{2}}} \right]\]
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