Consider the elementary reaction
X₂(g) → 2 X(g)
The potential-energy values (relative to the reactants) determined from computational chemistry are listed below.
• Energy of reactants (X₂): 0 kJ mol⁻¹
• Energy of transition state: +250 kJ mol⁻¹
• Energy of products (2 X): +200 kJ mol⁻¹
Use these data to analyze the reaction energetics.
(a) Determine each of the following. Show your work.
(i) The activation energy for the forward reaction
(ii) The activation energy for the reverse reaction
(iii) The overall energy change, ΔE, for the reaction
(b) Sketch a reaction energy profile consistent with the values calculated in part (a). Clearly label the axes, reactants, products, transition state, ΔE, Eₐ (forward), and Eₐ (reverse).
(c) Based on your sketch and calculations, state whether the reaction is endothermic or exothermic and justify your answer in terms of the relative energies of reactants and products.