Correct Option (C) 5 kJ mol–1
Explanation:
As ΔH is positive, therefore reaction is endothermic This is the energy profile diagram for an endothermic reaction. Now when the products is converted back to reactant the energy of activation is x as shown in fig. Evidently x = Ea – ΔH
= (77 – 72) = 5 kJ mol–1.