1. Generally, the rate of a reaction increases with increasing temperature. However, there are very few exceptions.
2. As a rough rule, for many reactions near room temperature, reaction rate tends to double when the temperature is increased by 10°C.
3. A large number of reactions are known which do not take place at room temperature but occur readily at higher temperature.
Example – Reaction between H2 and O2 to form H2O takes place only when an electric spark is passed.
4. Arrhenius suggested that the rates of most reactions vary with temperature in such a way that the rate constant is directly proportional to \(e^{-\frac{E_0}{RT}}\) and he proposed a relation between the rate constant and temperature.
k = \(Ae^{-\frac{E_0}{RT}}\)
where
k = frequency factor
R = gas constant ,
Ea = Activation energy
T = Absolute temperature (in kelvin)
The factor A does not vary significantly with temperature and hence it may be taken as a constant.
5. Taking logarithm on both side of the equation (1)
6. The plot of Ink vs \(\frac{1}{T}\) is a straight line with negative slope \(\frac{E_0}{Rt}\). If the rate constant for a reaction at two different temperatures is known, we can calculate the activation energy.
This equation can be used to calculate E from rate Ea constants k1 & k2 at temperature T1 and T2
