Chemical equilibrium is…………… by a catalyst.

Answer

**Step-by-Step Solution:**

1. **Understanding Chemical Equilibrium**: Chemical equilibrium occurs in a reversible reaction when the rate of the forward reaction equals the rate of the reverse reaction. At this point, the concentrations of the reactants and products remain constant.

2. **Role of a Catalyst**: A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. It does this by providing an alternative pathway with a lower activation energy for both the forward and reverse reactions.

3. **Effect of Catalyst on Reaction Rates**: When a catalyst is added to a reversible reaction, it increases the rates of both the forward and reverse reactions equally. This means that both the forward reaction (A → B) and the reverse reaction (B → A) will occur at an increased rate.

4. **Impact on Equilibrium**: Although the catalyst speeds up the rate at which equilibrium is reached, it does not change the position of the equilibrium itself. The concentrations of reactants and products at equilibrium remain the same as they would be without the catalyst.

5. **Conclusion**: Therefore, the statement can be completed as: "Chemical equilibrium is **unaffected** by a catalyst." The catalyst only helps the system reach equilibrium faster, but it does not alter the equilibrium concentrations.

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