Question

The activation energy of reactant molecules in a reaction depends upon:
A.Temperature
B.Nature of the reactants
C.Collision per unit time
D.Concentration of reactants

Answer 1

The activation energy is a stored form of energy present as the potential energy of the chemical bonds in the reactants and is often described as the minimum amount of energy required for a reaction to take place. It is calculated from the formula: ${\text{k}} = {\text{A}}{{\text{e}}^{ - \dfrac{{{E_a}}}{{{\text{RT}}}}}}$ where k is the rate constant, A is the Arrhenius Constant, ${E_a}$ is the activation energy, R is the universal gas constant, and T is the Kelvin temperature.

Complete step by step answer:
The minimum amount of energy required by a reactant to get converted into the product is called the “activation energy”. It is expressed in Joules, Kilojoules/mol, or kilocalorie/mol. The different factors that affect the activation energy of the molecules are:
1.Temperature: As a molecule gains energy, the speed of the molecule increases and hence the rate of collision increases. So the chances of attaining the activation energy also increases. But it does not have a direct influence.
2.Nature of the reactants: The nature of the reactant influences the activation energy. When the reactants are ions, there is attraction between them and the action energy required becomes higher.
3.Collision per unit time: The collisions between the molecules occurring per unit time increases the chances of the activation of the colliding molecules for the reaction to take place. But it does not have a direct influence.
4.Concentration of the reagents: The concentration of the reactants does not have any direct influence on the activation energy of the molecules.

Hence it can be said that, option (B) is the correct answer.

Note:
The activation energy depends on two factors only:
1.The nature of the reactant, because the reactant being an ionic or a covalent compound can determine the energy required for activation.
2.The presence of a catalyst in the medium also has an influence on the activation energy because the purpose of using the catalyst is to increase the rate of the reaction.