Question

For a reaction A\(\rightarrow\)B, the enthalpy of the reaction is −4.2 kJ mol⁻¹ and the enthalpy of activation is 9.6 kJ mol⁻¹. The correct potential energy profile for the reaction is shown in option

• A.
• B.
• C.
• D.

Answer 1

The Correct Option is C

To determine the correct potential energy profile for the reaction \(A \rightarrow B\), we need to understand the given information:

• The enthalpy change of the reaction (\(\Delta H\)) is −4.2 kJ/mol, which indicates that the reaction is exothermic (energy is released).
• The activation energy (\(E_a\)\)) is 9.6 kJ/mol, which is the energy difference between the reactants and the transition state.

In an exothermic reaction, the products have lower energy than the reactants, and the energy diagram will drop towards the products \(B\) after reaching the peak (the transition state).

The energy profile for this reaction should show:

1. An initial upward slope from reactants \(A\) showing the application of activation energy.
2. A peak representing the transition state.
3. A downward slope leading to the products \(B\), indicating that the products are at a lower energy level than the reactants due to the exothermic nature of the reaction.

The correct energy profile should match this description.

The above image correctly illustrates the potential energy profile for the reaction as described. The initial rise and subsequent fall represent the activation energy and the energy release in the reaction, respectively. Thus, this is the correct option.