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CAIE A Level Chemistry 9701 · Group 17

Group 17: suggest question

Suggest6 marksChallenge

A student heats separate samples of hydrogen chloride, hydrogen bromide and hydrogen iodide in sealed tubes and measures the temperature at which each begins to decompose into its elements. The student records the following decomposition temperatures:

  • hydrogen chloride: above 1500 °C
  • hydrogen bromide: about 900 °C
  • hydrogen iodide: about 300 °C

Suggest and explain the trend in thermal stability shown by these hydrogen halides.

0 words · 6 marks

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How this question is marked

6 marks, so the mark scheme is looking for about 6 separate creditworthy points. Making the same point twice in different words earns it once.

Suggest means: Apply what you know to an unfamiliar situation. There may be more than one acceptable answer. Reason from the principle you have learned to the new context, and say which principle you are using.

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