NEET Chemistry Notes Chemical Kinetics – Effect of Temperature on Rate of Reactions
Effect of Temperature on Rate of Reactions
Effect of Temperature on Rate of Reactions
It has been found that for a chemical reaction with rise in (temperature by 10°, the rate constant is nearly doubled. The temperature dependence of the rate of a chemical reaction can be accurately explained by Arrhenius equation
Temperature Coefficient
- It is the ratio of two rate constants differing by a temperature of 10 K.
- For most of the reactions, if temperature rises from 298 K to 308 K, the rate constant almost gets doubled.
- The value of temperature coefficient for most of the reactions lies between 2 to 3.
Activation Energy
It is represented by Ea. . It is constant for a particular reaction. Activation energy does not depend on temperature, volume, pressure etc., but gets affected by the presence of catalyst.
Catalyst increases the rate of reaction by providing alternative path of lower activation energy to the reactants.
Calculation of Activation Energy
Activation energy can be calculated by knowing the rate constants at two different temperatures, assuming that Ea and A remains constant.
Taking log both the sides in Arrhenius equation, we get
Now, if the values of rate constant at temperatures T1 ,T2 and k1 ,k2 respectively
This relation is used when rate constants at two different temperatures are given.
This reaction is also written as 
Arrhenius equation is purely an empirical equation that gives a reasonably good representation of temperature dependence of the rate constant.
When logic is plotted against 1/T, we get a straight line which is represented by Arrhenius equation as
Collision Theory
The collisions among the reacting species which result in the products are known as the effective collisions.
The species taking part in the chemical reaction must have a certain minimum energy known as threshold energy (E°).
