Which of the following will not change the concentration of ammonia at the equilibrium ?
Correct answer: C. Addition of catalyst
- A. Increase of pressure
- B. Increase of volume
- C. Addition of catalyst
- D. Decrease of temperature
Explanation
A catalyst speeds up both the forward and reverse reactions equally, so it does not shift equilibrium or change the equilibrium concentration of ammonia. Students often choose increase of pressure because pressure can affect ammonia concentration in the Haber equilibrium, but it does not leave it unchanged.
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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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