A LevelChemistryCIETopic Questions11. Group 1711.2 The Chemical Properties of the Halogen Elements & the Hydrogen Halides

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First teaching 2023

First exams 2025

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The Chemical Properties of the Halogen Elements & the Hydrogen Halides (CIE A Level Chemistry)

Topic Questions

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Medium
1a5 marks

Halogens react with hydrogen gas forming hydrogen halides.

 
i)
Write the equation for the reaction of bromine with hydrogen. State symbols are not required.
 
[1]
 
ii)
State the trend in thermal stability of the hydrogen halides down Group 17. Explain your answer. 
 
Trend ................................................................................
 
Explanation ................................................................................
 
[4]

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1b1 mark

In the reaction outlined in part (a), bromine, Br2, is acting as an oxidising agent. 


Order the halogens below from the weakest to strongest oxidising agent.

Bromine, Br2

Chlorine, Cl2

Iodine, I2

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1c3 marks

Explain why an iodide ion, I–, is a better reducing agent than a bromide ion, Br –.

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1a6 marks

A group of students are asked to determine the order of reactivity of the halogens and are provided with solutions of potassium chloride, potassium bromide and potassium iodide, as well as aqueous samples of each of the halogens. 

i)
Describe how the students would use the reagents named above to determine the trend in reactivity down Group 17 and give expected observations.

ii)
Suggest the trend that the students would find from their results.

iii)
Explain your answer to part (a)(ii), using relevant ionic equations. 

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1b1 mark

Suggest one extra reagent the students could use to make their observations more clear.

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1c4 marks

Halogens react with hydrogen gas to form hydrogen halides. Chlorine reacts with hydrogen when exposed to ultraviolet light to form hydrogen chloride.

i)
Write an equation for the reaction of chlorine and hydrogen.
[1]
ii)
Explain why the thermal stability of the hydrogen halides decreases down the group.
[3]

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2a2 marks

The hydrogen halides do not show perfect periodicity. A bar chart of boiling points, as seen in Fig. 2.1, shows that the boiling point of hydrogen fluoride, HF, is much higher than periodic trends would indicate.

3-2-ib-chemistry-sq-q1a-medium

Fig. 2.1 

Explain why the boiling point of HF is much higher than the boiling point of the other hydrogen halides.

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2b2 marks

There is an increase in boiling point moving from HCl to HI.

Explain this trend in boiling points of the hydrogen halides.

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2c2 marks

Explain why HF is more thermally stable than HI.

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3a4 marks

This question is about the reactions and properties of the elements in Group 17 of the Periodic Table. 

Define the term electronegativity and explain the trend in electronegativity seen down Group 17.

definition

explanation

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3b4 marks

Describe how an aqueous of solution of a halogen could be used to successfully distinguish between solutions containing potassium chloride, potassium bromide and potassium iodide. 

Provide relevant equations to justify your answer.

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3c3 marks

Bromine is used to extract iodine from a solution containing iodide ions.

Explain why iodine is a weaker oxidising agent than than bromine.

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