The energy changes during a reaction are shown by plotting potential energy against the reaction coordinate. What does the reaction coordinate represent?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → The profile of energy change when the reactants change into products
Along the reaction coordinate the system moves from the reactants, over the energy hump of the activated complex, down to the products. The plot therefore shows the energy barrier (activation energy) and the energy difference between reactants and products, step by step along the path of the change, not against time.
NCERT (2026-27 edition):
3.4 Temperature Dependence of the Rate of a Reaction – “Fig. 3.7 is obtained by plotting potential energy vs reaction coordinate. Reaction coordinate represents the profile of energy change when reactants change into products.”
Fig. 3.7: Diagram showing plot of potential energy vs reaction coordinate