Question: 65. Activation energy of any chemical reaction can be calculated if one knows the value of
(1) rate constant at standard temperature.
(2) probability of collision.
(3) orientation of reactant molecules during collision.
(4) rate constant at two different temperatures.
Answer: Option (4)
Explanation:
The relationship between the rate constant and temperature is given by the Arrhenius equation:
k = A e^{-E_a/RT}where k is the rate constant, A is the frequency factor,
E_a is the activation energy, R
is the gas constant and T is the absolute temperature.
If the rate constants at two different temperatures
T_1 and T_2 are known,
the Arrhenius equation can be written as:
\ln\left(\frac{k_2}{k_1}\right) = \frac{E_a}{R}\left(\frac{1}{T_1}-\frac{1}{T_2}\right)Using this equation, the value of activation energy E_a can be calculated.
Knowledge of rate constant at only one temperature, probability of collision, or orientation of reactant molecules is not sufficient to calculate activation energy.
Therefore, the activation energy of a reaction can be calculated if the rate constants at two different temperatures are known.
Hence, the correct answer is Option (4).