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Practice · Chemistry · 2025 syllabus · R1.3

IB Chemistry R1.3 Energy from fuels: practice questions

5 exam-style questions on R1.3 Energy from fuels, SL and HL: 3 multiple choice, 1 data-based and 1 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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R1.3-01 · Paper 1A style · multiple choice · 1 mark

Balancing a combustion equation

Butan-1-ol, C4H9OH, burns completely in oxygen. Balance the equation using the lowest possible whole-number coefficients. What do the coefficients add up to?
__C4H9OH + __O2 → __CO2 + __H2O [1]

  1. 15
  2. 16
  3. 32
  4. 33
Show the answer and the reasoning

Answer: B. B is correct. C4H9OH + 6O2 → 4CO2 + 5H2O. Oxygen on the right is 8 + 5 = 13 atoms; the alcohol supplies 1, so 12 come from 6 O2. Sum = 1 + 6 + 4 + 5 = 16. A (15) leaves out the unwritten coefficient 1. C (32) doubles every coefficient, which is not the smallest set. D (33) forgets the oxygen atom already in the alcohol: 6½ O2, doubled to 2 + 13 + 8 + 10.

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The 5 questions in R1.3

  1. R1.3-01 Balancing a combustion equationPaper 1A style · multiple choice · 1 mark
  2. R1.3-02 Products of incomplete combustionPaper 1A style · multiple choice · 1 mark
  3. R1.3-03 Electrodes in a fuel cellPaper 1A style · multiple choice · 1 mark
  4. R1.3-04 Specific energy of a liquid fuelPaper 1B style · data-based · 9 marks
  5. R1.3-05 Biofuels and combustionPaper 2 style · structured question · 6 marks

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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.