Class 12 Chemistry Chemical Kinetics | Activation energy |

__Activation energy__

- The minimum quantitiy of external energy required for the conversion of reactant into product or to produce an unstable intermediate is called activation energy. It is E
- Rate of reaction is inversely proportional to the activation energy.
- Therefore, greater value of activation energy leads to lower rate of reaction and increased influence of temperature change on the rate constant.

* PROBLEM*. The rate of the chemical reaction doubles for an increase of 10 K in absolute temperature from 298 K. Calculate E

** SOLUTION. **It is given that T

∴T2 = (298 + 10) K

= 308 K

We also know that the rate of the reaction doubles when temperature is increased by 10°.

Therefore, let us take the value of k_{1} = k and that of k_{2} = 2k

Also, R = 8.314 J K ^{- 1} mol ^{- 1}

Now, substituting these values in the equation:

Log k_{2}/k_{1} = E_{a}/2.303R [T_{2}-T_{1}/T_{1}T_{2}]

Log 2k/k = E_{a}/2.303 X 8.314 [10/298 X 308]

E_{a}= 2.303 X 8.314 X 298 X 308 X log2/10

= 52897.78 J mol^{ - 1}

= 52.9 kJ mol^{ - 1}

.