Which of the following statements is true regarding the energy diagram provided? 
i. The reaction is endothermic.
ii. Activation energy would be less than + 10 kJ after a catalyst is added.
iii. The reaction absorbs energy.
iv. Activation energy would be greater than + 10 kJ after a catalyst is added.

• A. I only
• B. II only
• C. I and III
• D. II, III and IV

Answer: (B)

Verified step by step guidance

1. Step 1: Analyze the energy diagram by comparing the enthalpy of reactants and products. The reactants start at about 40 kJ, and the products end at about 15 kJ, indicating a decrease in enthalpy. This means the reaction releases energy, so it is exothermic, not endothermic. Therefore, statement i is false.
2. Step 2: Understand that activation energy (Ea) is the energy difference between the reactants and the peak of the curve. From the graph, the peak is around 50 kJ, so Ea is approximately 10 kJ (50 kJ - 40 kJ).
3. Step 3: Consider the effect of a catalyst, which lowers the activation energy by providing an alternative pathway. Since the original Ea is about 10 kJ, adding a catalyst would reduce Ea to less than 10 kJ. This supports statement ii as true.
4. Step 4: Since the reaction releases energy (enthalpy decreases), it does not absorb energy overall. This means statement iii is false.
5. Step 5: Statement iv claims activation energy would be greater than 10 kJ after adding a catalyst, which contradicts the role of a catalyst. Therefore, statement iv is false.