The activation energy of a reaction is 3.5 kJ/mol and the change in enthalpy for the forward reaction is -67.2 kJ/mol. What is the activation energy of the reverse reaction?

• A. 70.7 kJ/mol
• B. 3.5 kJ/mol
• C. 67.2 kJ/mol
• D. 63.7 kJ/mol

Answer: (A)

Verified step by step guidance

1. Understand that the activation energy (Ea) is the minimum energy required for a reaction to occur. For a reverse reaction, the activation energy can be calculated using the enthalpy change (ΔH) of the forward reaction.
2. Recall that the enthalpy change (ΔH) for a reaction is the difference in energy between the products and reactants. A negative ΔH indicates an exothermic reaction, where energy is released.
3. Use the relationship between the activation energy of the forward reaction (Ea_forward), the activation energy of the reverse reaction (Ea_reverse), and the enthalpy change (ΔH): Ea_reverse = Ea_forward + |ΔH|.
4. Substitute the given values into the equation: Ea_reverse = 3.5 kJ/mol + |-67.2 kJ/mol|.
5. Calculate the absolute value of the enthalpy change and add it to the activation energy of the forward reaction to find the activation energy of the reverse reaction.