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CAIE A Level Chemistry 9701

Group 17 questions

Exam-style questions on Group 17, ordered from foundation to challenge. Pick one, write your answer the way you would in the exam, and it comes back marked against the mark scheme, point by point.

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Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.

  1. Explain4 marksStandardA student investigates the reactions of chlorine, bromine and iodine with hydrogen. Chlorine reacts explosively in sunlight, bromine reacts slowly when heated, and iodine reacts only at high temperatures and the…
  2. Explain4 marksStandardThe hydrogen halides are HF, HCl, HBr and HI. Their thermal stability decreases down the group: HF is the most stable and HI is the least stable. Explain this trend in terms of bond strengths.
  3. Suggest4 marksStandardA student heats samples of hydrogen chloride, hydrogen bromide and hydrogen iodide in separate sealed tubes. State which of these hydrogen halides is the most thermally stable and explain why, in terms of bond strength.
  4. Describe5 marksStandardA small volume of potassium chloride solution is added to aqueous silver nitrate. The precipitate formed is then treated with aqueous ammonia. In a separate experiment, solid potassium chloride is warmed with an excess…
  5. Compare5 marksStandardFluorine and iodine are halogens at opposite ends of Group 17. Compare the reactivity of fluorine and iodine as oxidising agents, their reactions with hydrogen, and the thermal stability of the hydrogen halides formed…
  6. Compare5 marksStandardCompare the reactions of chloride, bromide, and iodide ions with concentrated sulfuric acid. Include balanced chemical equations and explain the trend in reducing ability of the halide ions.
  7. Explain4 marksStandardIn the treatment of drinking water, chlorine gas is added to kill harmful bacteria. Explain, using relevant equations and oxidation numbers, how chlorine produces the active disinfecting species HOCl and ClO- in water…
  8. Explain4 marksStandardThe table shows the boiling points and bond dissociation energies of chlorine, bromine and iodine. Halogen Colour Boiling point / °C Bond dissociation energy / kJ mol⁻¹ Cl2 pale green –34 242 Br2 red-brown 59 193 I2…
  9. Suggest4 marksStandardChlorine, bromine and iodine are molecular elements. Their boiling points are –34 °C, 59 °C and 184 °C respectively. Suggest, in terms of the structure and bonding of the molecules, why the boiling points increase from…
  10. Describe5 marksStandardAt room temperature, chlorine is a pale green gas, bromine is a red-brown liquid and iodine is a grey-black solid. Describe the trend in volatility of chlorine, bromine and iodine, and explain this trend in terms of…
  11. Explain4 marksStandardA student investigates the reducing ability of halide ions. In one test, aqueous sodium chloride, sodium bromide and sodium iodide are each added to acidified silver nitrate solution. In a second test, each halide is…
  12. Suggest4 marksStandardAt 298 K and 1 atm pressure, chlorine is a gas, bromine is a liquid and iodine is a solid. Suggest explanations for: (a) the trend in volatility of chlorine, bromine and iodine; (b) the trend in the strength of the…
  13. Compare5 marksStandardChlorine reacts with hydrogen in sunlight to form hydrogen chloride. Iodine reacts with hydrogen only when heated strongly, and the reaction is reversible. Compare the reactions of chlorine and iodine with hydrogen…
  14. Compare5 marksStandardCompare the volatility of chlorine, bromine and iodine with the strength of the covalent bond in each molecule. Include the colours of the three elements in your answer.
  15. Compare5 marksStandardTable 1 shows some physical properties of chlorine, bromine and iodine. Halogen Boiling point / °C Bond dissociation energy / kJ mol⁻¹ Chlorine, Cl₂ –34 242 Bromine, Br₂ 59 193 Iodine, I₂ 184 151 Compare the volatility…
  16. Compare5 marksStandardA student has an aqueous solution of a sodium halide, NaX, where X is a halogen. In one test, acidified aqueous silver nitrate is added, producing a cream precipitate that dissolves when dilute aqueous ammonia is…
  17. Explain4 marksStandardA student added concentrated sulfuric acid to separate solid samples of sodium chloride, sodium bromide and sodium iodide. The results are shown. Halide Observations with conc. H2SO4 Result of adding aqueous AgNO3 to…
  18. Compare5 marksStandardThe bond energies of the hydrogen–halogen bonds are: H–F 562 kJ mol⁻¹, H–Cl 431 kJ mol⁻¹, H–Br 366 kJ mol⁻¹, H–I 299 kJ mol⁻¹. Compare the thermal stabilities of the hydrogen halides and explain the trend in terms of…
  19. Compare5 marksStandardChlorine reacts with cold and hot aqueous sodium hydroxide to produce different products. Compare these two reactions in terms of the products formed and the changes in oxidation number of chlorine. Include balanced…
  20. Explain4 marksStandardChlorine, bromine and iodine are all simple molecular substances. Their boiling points are –34 °C, 59 °C and 184 °C respectively. Explain, in terms of structure and bonding, why the boiling point increases from…
  21. Describe5 marksStandardA student adds aqueous solutions of chlorine, bromine and iodine separately to aqueous potassium iodide, aqueous potassium bromide and aqueous potassium chloride. The student records whether a reaction occurs and the…
  22. Suggest4 marksStandardIn water treatment, chlorine is added to water. In the water, chlorine undergoes disproportionation to form chloride ions and chloric(I) acid, HOCl. HOCl is a weak acid that partially dissociates to form H+ and ClO−…
  23. Compare5 marksStandardChlorine, bromine and iodine are the first three elements in Group 17. At room temperature, chlorine is a gas, bromine is a liquid and iodine is a solid. Compare the volatility and the bond strength of these three…
  24. Suggest4 marksStandardA student adds aqueous chlorine to separate solutions containing iodide ions and bromide ions. In a second experiment, aqueous iodine is added to a solution containing bromide ions. Suggest what is observed in each…
  25. Suggest4 marksStandardA colourless solution contains one halide ion. A student adds aqueous silver nitrate and observes a cream precipitate. Addition of dilute aqueous ammonia does not dissolve the precipitate, but addition of concentrated…
  26. Suggest4 marksStandardA student adds separate samples of sodium chloride, sodium bromide and sodium iodide to three test tubes, each containing an equal volume of concentrated sulfuric acid. The student observes the colour of any gas…
  27. Describe5 marksChallengeA student adds solid sodium chloride to an excess of cold concentrated sulfuric acid. The mixture effervesces and a misty white fume is seen. The student writes the equation: NaCl(s) + H2SO4(l) → NaHSO4(s) + HCl(g) The…
  28. Describe7 marksChallengeDescribe the relative reactivity of the chloride, bromide and iodide ions as reducing agents. Explain how this trend is demonstrated by the reactions of aqueous solutions of sodium chloride, sodium bromide and sodium…
  29. Describe6 marksChallengeAt room temperature, chlorine is a pale green gas, bromine is a dark red-brown liquid and iodine is a grey-black solid. Describe the trend in volatility of these three elements and explain this trend in terms of the…
  30. Describe5 marksChallengeChlorine, bromine and iodine are halogens. Their boiling points are –34 °C, 59 °C and 184 °C respectively. Describe and explain the relative volatility of chlorine and iodine, and explain the relative strength of the…
  31. Describe5 marksChallengeIn an industrial process, hydrogen gas is passed over heated iodine to form hydrogen iodide. The reaction is reversible and reaches equilibrium: H2(g) + I2(g) ⇌ 2HI(g) (a) Describe the trend in reactivity of the…
  32. Explain5 marksChallengeThe boiling points of the halogens increase down Group 17: chlorine boils at −34 °C, bromine at 59 °C and iodine at 184 °C. Explain this trend, referring to the intermolecular forces involved.
  33. Compare7 marksChallengeThe hydrogen halides HF, HCl, HBr and HI can be formed by direct combination of the elements. Samples of each hydrogen halide are heated in separate sealed tubes and the temperature at which each begins to decompose…
  34. Explain5 marksChallengeThe elements of Group 17 react with hydrogen to form hydrogen halides, and the hydrogen halides decompose on heating. (a) State and explain the trend in the oxidising power of the halogen elements down the group. (b)…
  35. Explain7 marksChallengeFluorine reacts with hydrogen even in the dark at room temperature, whereas chlorine requires light or a flame, and iodine only reacts slowly when heated. The hydrogen halides formed decompose on heating, and their…
  36. Compare7 marksChallengeChlorine, bromine and iodine are molecular elements. In terms of their electron arrangements and the forces between their molecules, compare their volatility and the strength of the covalent bond within each molecule.
  37. Describe7 marksChallengeChlorine undergoes different reactions with cold and hot aqueous sodium hydroxide and is also used in water purification. (a) Describe, with equations, the reactions of chlorine with cold and with hot aqueous sodium…
  38. Suggest6 marksChallengeBromine is a liquid at room temperature and pressure, whereas chlorine is a gas. Suggest why bromine has a higher boiling point than chlorine, referring to the intermolecular forces involved.
  39. Describe7 marksChallengeThe elements chlorine, bromine and iodine exist as diatomic molecules at room temperature. The table below shows their boiling points. Element Boiling point / °C Chlorine –34 Bromine 59 Iodine 184 (a) State the colour…
  40. Suggest6 marksChallengeA 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…
  41. Describe7 marksChallengeThe table shows the bond dissociation energies of hydrogen chloride and hydrogen bromide. Bond Bond dissociation energy / kJ mol⁻¹ H–Cl 431 H–Br 366 (a) Describe the relative reactivities of chlorine and bromine as…
  42. Compare7 marksChallengeA student is given a colourless solution thought to contain a halide salt. A sample is acidified with dilute nitric acid and then aqueous silver nitrate is added. A pale yellow precipitate forms. The precipitate does…
  43. Explain7 marksChallengeA student is given two colourless solutions, one containing bromide ions and the other containing iodide ions. Concentrated sulfuric acid is added separately to each solution. The bromide mixture produces a pungent gas…