Le Chatelier's Principle and Reaction Rates in Exothermic Reactions

Steps:

• The reaction is exothermic (ΔH < 0), so decreasing temperature from 450°C to 250°C shifts equilibrium right, increasing SO₃ yield.
• Removing the catalyst does not affect equilibrium position, only rate.
• Lower temperature slows molecular collisions, decreasing reaction rate.
• Removing catalyst increases activation energy barrier, further decreasing rate.

Why C is correct:

• Equilibrium yield increases due to Le Chatelier's principle for exothermic reactions; rate decreases from both lower temperature and catalyst removal.

Why the others are wrong:

• A: Yield increases, not decreases; rate decreases, not no change.
• B: Yield increases, not decreases; rate decreases but paired wrongly.
• D: Rate decreases, not increases.

Final answer: C