Question

Activation energy of a chemical reaction can be determined by
A. Determining the rate constant at standard temperature
B. Determining the rate constant at two temperatures
C. Determining probability of collision
D. Using catalyst

Answer 1

Hint: The calculation of activation energy can be done by various methods full stop; it can be calculated by using Arrhenius equation and also if two temperatures and rate constant at both temperatures is known.

Complete answer:
The activation energy of a reaction refers to the minimum amount of energy which is required for the reaction to occur. If the need of activation energy is not met in a reaction the process did not get successful, that is the reaction does not occur. Activation energy is the term introduced by a scientist Svante Arrhenius from Sweden. He gave an equation which relates the activation energy E with the rate of a reaction.
Activation energy is also calculated by using rate constants known at two different temperatures. Let us consider the following equation for the above purpose,
\[ln({{k}_{2}})-\ln ({{k}_{1}})=\left( \ln (A)-\dfrac{Ea}{R{{T}_{2}}} \right)\left( \ln (A)-\dfrac{Ea}{R{{T}_{2}}} \right)\]
=\[\dfrac{Ea}{R}\left( \dfrac{1}{{{T}_{1}}}-\dfrac{1}{{{T}_{2}}} \right)\]
Here \[\ln (k)=\dfrac{Ea}{Rt}+\ln (A)\]
In the presence of a catalyst, the activation energy gets lowered because the catalyst increases the rate of the chemical reaction, slower the chemical reaction the higher will be its activation energy. The release of heat also lowers the activation energy required by the reaction.

The correct answer is (B).

Note: The activation energy makes the movements in the reactants and enables them to overcome their repulsive forces and break bonds to form products.
If activation energy becomes zero there will be no effective collisions and no product formation. The temperature should be converted in kelvin for the calculation of activation energy using above methods.