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Practice · Chemistry · 2025 syllabus · R1.4

IB Chemistry R1.4 Entropy and spontaneity: practice questions

7 exam-style questions on R1.4 Entropy and spontaneity, HL only: 4 multiple choice and 3 structured. Each one comes with the mark scheme, a model answer and the reasoning behind every mark. Free with your email.

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R1.4-01 · Paper 1A style · multiple choice · 1 mark · HL

Spotting an entropy decrease

In which change does the entropy of the system decrease? [1]

  1. NH4Cl(s) → NH4Cl(aq)
  2. 2NO2(g) → N2O4(g)
  3. CaCO3(s) → CaO(s) + CO2(g)
  4. H2O(l) → H2O(g)
Show the answer and the reasoning

Answer: B. B is correct. Two moles of gas become one, so there are fewer ways to arrange the particles and entropy falls. A: dissolving spreads the ions out, so entropy rises. C produces a gas from a solid. D: a liquid turning to gas is a large entropy increase.

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The 7 questions in R1.4

  1. R1.4-01 Spotting an entropy decreasePaper 1A style · multiple choice · 1 mark · HL
  2. R1.4-02 Spontaneous at every temperaturePaper 1A style · multiple choice · 1 mark · HL
  3. R1.4-03 The changeover temperaturePaper 1A style · multiple choice · 1 mark · HL
  4. R1.4-04 Largest entropy increasePaper 1A style · multiple choice · 1 mark · HL
  5. R1.4-05 Hydrogenating ethene: ΔS, ΔG and TPaper 2 style · structured question · 7 marks · HL
  6. R1.4-06 From ΔG to K and directionPaper 2 style · structured question · 5 marks · HL
  7. R1.4-07 Minimum temperature for a kilnPaper 2 style · structured question · 5 marks · HL

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Every Biology and Chemistry question here is original, written for practice in the style of the papers set since the 2025 syllabus, with invented data. Developed independently from the International Baccalaureate Organization, which has not endorsed it. Found a mistake? Email vytis@limeadmissions.com with the question id.