The activation energy for the reaction NO2(g) + CO(g) → NO(g) + CO2(g) is Ea = 100 kJ/mol and the change in enthalpy for the reaction is ΔH = -250 kJ/mol. What is the activation energy for the reverse reaction?

• A. 100 kJ/mol
• B. 250 kJ/mol
• C. 350 kJ/mol
• D. 150 kJ/mol

Answer: (C)

Verified step by step guidance

1. Understand that the activation energy (Ea) is the minimum energy required for a reaction to occur. For the forward reaction, Ea is given as 100 kJ/mol.
2. Recognize that the change in enthalpy (ΔH) is the difference in energy between the products and reactants. Here, ΔH is -250 kJ/mol, indicating that the reaction is exothermic.
3. For the reverse reaction, the activation energy can be calculated by adding the absolute value of ΔH to the activation energy of the forward reaction. This is because the reverse reaction must overcome both the energy released in the forward reaction and the original activation energy.
4. Express the relationship mathematically: Ea(reverse) = Ea(forward) + |ΔH|.
5. Substitute the given values into the equation: Ea(reverse) = 100 kJ/mol + 250 kJ/mol.