In a standard potential energy diagram for a single-step reversible reaction , the forward activatio — Chemical Kinetics Chemistry Question
Question
In a standard potential energy diagram for a single-step reversible reaction $R \rightleftharpoons P$, the forward activation energy $E_{a(f)}$ is mapped as $13 \text{ kJ/mol}$ and the backward activation energy $E_{a(b)}$ is $8 \text{ kJ/mol}$. If the absolute potential energy of the ground-state reactant species $R$ is independently evaluated at $10 \text{ kJ/mol}$, what is the exact Threshold Energy of this reaction pathway?
💡 Solution & Explanation
The Threshold Energy represents the absolute peak potential energy required for the reactants to reach the transition state/activated complex. It is calculated by adding the baseline potential energy of the reactants to the forward activation energy barrier. Threshold Energy $= \text{P.E.}_{\text{Reactant}} + E_{a(f)} = 10 \text{ kJ/mol} + 13 \text{ kJ/mol} = 23 \text{ kJ/mol}$.