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Difficulty: EasyLe Chatelier's Principle
Consider the reversible industrial reaction represented by the thermochemical equation below:
CO(g)+2H2(g)⇌CH3OH(g)ΔH=−90 kJ mol−1CO(g) + 2H_2(g) \rightleftharpoons CH_3OH(g) \quad \Delta H = -90\text{ kJ mol}^{-1}
What is the effect of adding a suitable catalyst to this equilibrium mixture?
  1. It has no effect on the equilibrium position.Answer
  2. B
    It shifts the equilibrium position to the right to increase methanol yield.
  3. C
    It shifts the equilibrium position to the left to favor the reactants.
  4. D
    It increases the yield of methanol by lowering the activation energy of the forward reaction only.

Answer

Adding a catalyst has no effect on the equilibrium position.
A catalyst provides an alternative pathway with lower activation energy for both the forward and reverse reactions. As a result, both rates are increased equally, allowing dynamic equilibrium to be reached faster without changing the relative amounts of reactants and products at equilibrium.

Step-by-Step Solution

1
Analyze the fundamental action of a catalyst in a chemical system.
A catalyst lowers the activation energy for both the forward and reverse reactions by providing an alternative reaction pathway.
Lowering the activation energy increases the rate of reaction in both directions by the exact same proportion.
2
Apply Le Chatelier's principle and equilibrium concepts to assess position shift.
The equilibrium position and the equilibrium concentrations of reactants and products remain unaffected.
Because both forward and reverse rates accelerate equally, the system reaches dynamic equilibrium faster without altering the final yield.

Key Concept

Effect of a catalyst on chemical equilibrium
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Topics

Le Chatelier's Principle

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