OCR A-Level Chemistry AS Breadth in chemistry (01), June 2025: Question 13

✅ Correct Answer

B: The position of equilibrium moves towards the products.

A catalyst never alters the position of dynamic equilibrium or changes the equilibrium yield. It increases the rate of both forward and backward reactions by the exact same factor. Therefore, statement B is scientifically incorrect and cannot be a benefit.

💡 Key Knowledge

• How catalysts work: They provide an alternative reaction route with a lower activation energy (E_a).
• Effect on equilibrium: A catalyst speeds up forward and reverse reactions equally. It allows equilibrium to be reached faster, but has no effect on the position of equilibrium.
• Sustainability benefits of catalysts:
  • Allows reactions to run at lower temperatures and pressures (reduces energy demand).
  • Less fossil fuel combustion means lower CO₂ emissions.
  • Gives a faster reaction rate (less production time), leading to higher throughput.

🧠 Exam Technique: Negative Phrasing

• Watch the bold word: Notice that the question asks which statement is not a benefit.
• Filter true vs. false:
  • A (True benefit): Lower activation energy means lower temperatures are viable.
  • B (Chemically false): Catalysts cannot shift equilibrium. This immediately flags it as the correct option.
  • C (True benefit): Higher rate = quicker completion time.
  • D (True benefit): Operating at lower temperatures directly cuts electrical/heating energy demand.

❌ Common Errors

• Confusing Rate with Yield: Thinking that because a catalyst speeds up the reaction, it must also produce more product at equilibrium.
• Misreading the question: Skipping past the word not and selecting A or D simply because they are well-known true facts about catalysts.
• Equilibrium misconception: Believing catalysts only affect the forward reaction. Remember: the activation energy is lowered identically for both forward and reverse directions.