Consider the reaction : 2SO2 + O2 ............. 2SO3 + Heat will be maximum if :
Correct answer: C. Temperature is decreased and pressure is increased
- A. Both pressure and temperature are increased
- B. Both pressure and temperature are decreased
- C. Temperature is decreased and pressure is increased
- D. Temperature is increased and pressure is increased
Explanation
The reaction 2SO2 + O2 → 2SO3 is exothermic, releasing heat. According to Le Chatelier's principle, increasing pressure shifts the equilibrium towards the side with fewer moles of gas, which is the forward reaction. Increasing temperature enhances the reaction rate by providing more energy to overcome activation energy. Therefore, the reaction rate and product formation are maximized when both pressure and temperature are increased.Options A and C, although they involve increasing pressure, do not involve increasing temperature, which is necessary to maximize the reaction rate. Option B decreases both pressure and temperature, which is counterproductive to both reaction rate and product formation.
This question appeared on the ETEA MDCAT 2008 paper, which you can sit online with every answer explained.
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About Le Chatelier's Principle
Le Chatelier's principle predicts how an equilibrium responds when concentration, pressure or temperature changes. Questions apply it to reversible reactions, identify the direction of shift and distinguish genuine equilibrium changes from the effect of a catalyst, which changes the rate of reaching equilibrium but not its position.
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