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Practice · Chemistry · 2025 syllabus · R2.3

IB Chemistry R2.3 How far? The extent of chemical change: practice questions

10 exam-style questions on R2.3 How far? The extent of chemical change, SL and HL, 5 marked HL: 6 multiple choice, 1 data-based 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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R2.3-01 · Paper 1A style · multiple choice · 1 mark

Heating an endothermic equilibrium

N2O4(g) ⇌ 2NO2(g), ΔH = +57 kJ mol−1. What happens to the position of equilibrium and to K when the temperature is raised? [1]

  1. Shifts left; K decreases
  2. Shifts right; K does not change
  3. Shifts right; K increases
  4. Shifts left; K does not change
Show the answer and the reasoning

Answer: C. C is correct. Raising the temperature favours the endothermic direction, here the forward reaction, so more NO2 forms and K increases. B is the trap: K is unchanged by pressure, concentration or a catalyst, but a temperature change always changes K. In May 2025, 30 % of candidates predicted the shift correctly but did not know that only temperature changes K. A and D treat the reaction as exothermic.

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The 10 questions in R2.3

  1. R2.3-01 Heating an endothermic equilibriumPaper 1A style · multiple choice · 1 mark
  2. R2.3-02 K for the reverse reactionPaper 1A style · multiple choice · 1 mark
  3. R2.3-03 What dynamic equilibrium meansPaper 1A style · multiple choice · 1 mark
  4. R2.3-04 Comparing Q with KPaper 1A style · multiple choice · 1 mark · HL
  5. R2.3-05 K from equilibrium amountsPaper 1A style · multiple choice · 1 mark · HL
  6. R2.3-06 What K at two temperatures showsPaper 1A style · multiple choice · 1 mark
  7. R2.3-07 Equilibrium constant by colorimetryPaper 1B style · data-based · 6 marks · HL
  8. R2.3-08 Compressing an equilibrium mixturePaper 2 style · structured question · 6 marks
  9. R2.3-09 K, ΔG and the extent of reactionPaper 2 style · structured question · 6 marks · HL
  10. R2.3-10 Which way will it go?Paper 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.