Two single-step reactions, Reaction 1 and Reaction 2
CHEMISTRY · Multi-part · CBSE · Chemistry · Chemical Kinetics · Chemical Kinetics
Problem
Two single-step reactions, Reaction 1 and Reaction 2, are carried out at 298 K. The potential-energy profiles are described below.
• Reaction 1: The reactants are assigned a potential energy of 0 kJ mol⁻¹. The transition state occurs at +80 kJ mol⁻¹, and the products lie at –40 kJ mol⁻¹.
• Reaction 2: The reactants are also assigned 0 kJ mol⁻¹. The transition state occurs at +45 kJ mol⁻¹, and the products lie at +25 kJ mol⁻¹.
Answer the following questions about the two reactions.
(a) Identify which reaction is exothermic and which is endothermic. Support your answer with appropriate reasoning based on the given energy values.
(b) Compare the activation energies of the two reactions and determine which reaction is expected to proceed more rapidly at 298 K. Justify your choice.
(c) The magnitude of the enthalpy change differs for the two reactions. Explain whether the magnitude of ΔH alone can be used to predict reaction rate. Provide an argument that references features of the energy diagrams.