A potential-energy profile for an elementary reaction shows that the reactants rise…
CHEMISTRY · Single correct · A Level · Chemistry · Energetics · Energetics
Problem
A potential-energy profile for an elementary reaction shows that the reactants rise 150 kJ·mol⁻¹ to reach the transition state and the products lie 200 kJ·mol⁻¹ below the reactants.
Which statement is most consistent with these data?
(a) Adding the 150 kJ·mol⁻¹ needed to reach the transition state to the 200 kJ·mol⁻¹ change afterwards gives a net enthalpy change of +50 kJ·mol⁻¹, so the reaction is endothermic.
(b) Because the activation energy is 150 kJ·mol⁻¹, which is greater than zero, the reaction must be endothermic.
(c) More energy is released when product bonds form than is required to break reactant bonds, so the reaction is exothermic.
(d) Product bonds are stronger than reactant bonds, meaning extra energy is required to form them; therefore, energy is absorbed from the surroundings.