UK Chemistry Olympiad

Enthalpy and the chemistry of matches | Chemistry Olympiad worked answers

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A close-up photograph of a brown match head held against the side of a match box ready to be struck

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Try this worked example of a Chemistry Olympiad question on enthalpy change and the chemistry behind matches. Includes video walkthrough and transcript.

In this question from the 2009 UK Chemistry Olympiad round one paper, students learn about the reaction that takes place when a match is struck. They write equations for the combustion of phosphorus sesquisulfide, as well as the decomposition of potassium chlorate(V), before turning to the reaction between these two substances and calculating a mass ratio and enthalpy change. They then compare the structures of various phosphorus sulfides as determined by NMR spectroscopy.

The accompanying video walkthrough is designed to help students if they get stuck or want to check their working.

This question is of moderate difficulty, and covers the following chemistry topics:

  • Balancing equations
  • Mole calculations
  • Enthalpy calculations
  • NMR spectroscopy

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