Adding a catalyst to a system at equilibrium
Correct answer: D. speeds up the forward and reverse reactions equally, so equilibrium is reached sooner but is unchanged
- A. shifts the equilibrium towards the products
- B. shifts the equilibrium towards the reactants
- C. increases the value of Kc
- D. speeds up the forward and reverse reactions equally, so equilibrium is reached sooner but is unchanged
Explanation
A catalyst lowers the activation energy of both directions by the same amount, so both rates rise in proportion and they still become equal at exactly the same position. What changes is the time taken to get there, which is commercially vital in a process such as the Haber synthesis. Only temperature changes the value of Kc itself.
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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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