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Reviewed CSCA Chemistry question · Standard

For the reaction N2(g) + 3H2(g) ⇌ 2NH3(g) at equilibrium, which change will shift the equilibrium to the right (toward products)?

  1. Increasing the volume of the container
  2. Decreasing the concentration of N2
  3. Increasing the concentration of NH3
  4. Decreasing the volume of the container
Show the answer and explanation

Correct answer

D. Decreasing the volume of the container

Principle or equation

Le Chatelier's principle: for a gaseous equilibrium, decreasing volume increases pressure, shifting equilibrium toward the side with fewer moles of gas. Here, product side has 2 moles, reactant side has 4 moles, so shift right.

Why this answer is correct

Increasing volume decreases pressure, shifting toward more moles (left). Decreasing N2 shifts left. Increasing NH3 shifts left. Decreasing volume increases pressure, shifting toward fewer moles, which is the product side (2 mol vs 4 mol), so equilibrium shifts right.

Example

For 2A(g) ⇌ B(g), decreasing volume shifts right because product side has fewer moles.

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