Question

The activation energy of forward and backward reaction for an endothermic reaction ${\text{X}} \to {\text{Y + Z}}$ are ${{\text{E}}_{\text{f}}}$ and ${{\text{E}}_{\text{b}}}$ respectively then,
1. ${{\text{E}}_{\text{b}}}$= ${{\text{E}}_{\text{f}}}$
2. ${{\text{E}}_{\text{b}}}$ < ${{\text{E}}_{\text{f}}}$
3. ${{\text{E}}_{\text{b}}}$ > ${{\text{E}}_{\text{f}}}$
4. Anyone of the above

Answer 1

Hint: Activation energy of a chemical reaction is the amount of energy required to start a chemical reaction, activation energy is less for a spontaneous reaction and is high for a non-spontaneous reaction. Lesser the activation energy faster will be the rate of a reaction. A catalyst can be used to reduce the activation energy.

Complete Step by step answer: The reaction given in the question has the forward and backward reaction energy as ${{\text{E}}_{\text{f}}}$ and ${{\text{E}}_{\text{b}}}$ respectively. ${\text{X}} \to {\text{Y + Z}}$
Now, since the reaction is an endothermic one, it would consume energy during its course of action, this implies that for the endothermic reaction the forward energy (${{\text{E}}_{\text{f}}}$) will be higher.
And since we need to give energy for the reaction to occur this could mean that the reactant undergoing reaction is more stable than the product formed, hence we can conclude that the backward reaction energy (${{\text{E}}_{\text{b}}}$) will be less
Therefore, we can say ${{\text{E}}_{\text{b}}}$ < ${{\text{E}}_{\text{f}}}$

Hence, the correct answer is option (2) .

Note: The clear knowledge of exothermic and endothermic reactions is the key to solve these types of questions. Catalyst can only catalyze a spontaneous reaction, it cannot catalyze a non-spontaneous reaction. it does not alter the Gibbs free energy of a reaction.