Unit 5: Reactivity 2: How Much, How Fast and How Far?
Topic 5.3: How Far? The Extent of Chemical Change Questions
Practice 20 exam-style questions for IB Chemistry Topic 5.3. Review the question stems below, then unlock the full Question Bank to access markschemes, model answers, and AI grading.
1State1 mark
Write the equilibrium constant expression, , for the equilibrium 2NO(g) + O₂(g) ⇌ 2NO₂(g).
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2026
Draw a graph showing how the rates of the forward and reverse reactions change as a system reaches dynamic equilibrium.
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Explain why Kc changes with temperature but not with concentration or pressure.
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Explain the effect of raising the temperature on the yield of ammonia.
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Deduce the effect of increasing the pressure on the yield of ammonia.
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Discuss why the Haber process is operated at about 450 °C rather than at a lower temperature.
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2026
Draw a graph of concentration against time showing what happens.
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State Le Châtelier's principle and use it to predict the effect of adding more reactant to a system at equilibrium.
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Explain why adding a catalyst to a system at equilibrium does not change the position of equilibrium, and state what it does change.
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Unlock Question11predict3 marks
For the equilibrium 2NO₂(g) ⇌ N₂O₄(g), ΔH = −57 kJ mol⁻¹, NO₂ is brown and N₂O₄ is colourless. Predict and explain the colour change seen when the mixture is cooled.
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Unlock Question12calculate3 marks
For the equilibrium A(g) + B(g) ⇌ 2C(g), the equilibrium concentrations are [A] = 0.20, [B] = 0.30 and [C] = 0.60 mol dm⁻³. Calculate Kc and state its units.
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State what a value of Kc much greater than 1 tells you about a reaction at equilibrium, and state whether Kc is affected by adding a catalyst.
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For N₂O₄(g) ⇌ 2NO₂(g), ΔH is positive. Explain what happens to the value of Kc when the temperature is increased.
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Write the equilibrium constant expression, Kc, for 2SO₂(g) + O₂(g) ⇌ 2SO₃(g), and explain why the concentration of a pure solid would be omitted from such an expression.
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State the two characteristics of a system at dynamic equilibrium, and explain why it is described as dynamic.
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State the condition a system must satisfy before it can reach equilibrium, and explain why an open beaker of reacting acid and carbonate does not.
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Describe how the rates of the forward and reverse reactions change from the moment reactants are mixed until equilibrium is reached.
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Explain why a reaction at equilibrium shows no visible change even though both reactions are still occurring.
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2026
Which statement about a system at dynamic equilibrium is correct?
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