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Cambridge International AS & A Level Chemistry

Topic 11
Group 17

Topic 11 covers the colours, volatility and bond strengths of chlorine, bromine and iodine, their relative reactivity as oxidising agents including the reactions with hydrogen and the thermal stability of the hydrogen halides, the halide ions as reducing agents with silver ions, ammonia and concentrated sulfuric acid, and the disproportionation reactions of chlorine with cold and hot sodium hydroxide and in water purification.

Exam Papers
Papers 1 & 2
9701 AS Level
Learning Outcomes
11.1 – 11.4
10 outcomes covered
Topic Parts
4 pages
Revision notes available
Exam Board
Cambridge
9701 (2025 onwards)

Revision Notes

Work through Topic 11 Group 17 in a structured sequence.

F₂ to I₂
Halogen
Trends
1
Available

Trends in the Halogens

The trends in Group 17: states, colours, boiling points, electronegativity, reactivity and predictions for fluorine and astatine.

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Displacement
Oxidising
Agents
2
Available

Halogens as Oxidising Agents

The halogens as oxidising agents: displacement reactions, colours in water and cyclohexane, reactions with metals and hydrogen, and the reactivity trend.

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Water and bleach
Chlorine
Reactions
3
Available

Disproportionation Reactions of Chlorine

The disproportionation of chlorine with water and with cold and hot alkali, bleach, water treatment and analogous halogen reactions.

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Cl⁻, Br⁻, I⁻
Halide
Ions
4
Available

Halide Ions: Reducing Agents and Tests

Halide ions: reducing power with concentrated sulfuric acid, the acidified silver nitrate test and ammonia, and the hydrogen halides with ammonia and water.

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Specification Coverage

Topic 11 Group 17 – Cambridge International AS Level Chemistry

The following Cambridge learning outcomes state what candidates should be able to do. Wording is taken from the Cambridge International AS & A Level Chemistry (9701) syllabus.

11.1 Physical properties of the Group 17 elements

11.1.1
describe the colours and the trend in volatility of chlorine, bromine and iodine
11.1.2
describe and explain the trend in the bond strength of the halogen molecules
11.1.3
interpret the volatility of the elements in terms of instantaneous dipole–induced dipole forces

11.2 The chemical properties of the elements and their hydrides

11.2.1
describe the relative reactivity of the elements as oxidising agents
11.2.2
describe and explain the reactions of the elements with hydrogen
11.2.3
describe and explain the relative thermal stabilities of the hydrogen halides in terms of bond strengths

11.3 Some reactions of the halide ions

11.3.1
describe the relative reactivity of halide ions as reducing agents
11.3.2
describe and explain the reactions of halide ions with:
a
aqueous silver ions followed by aqueous ammonia
b
concentrated sulfuric acid, to include balanced chemical equations

11.4 The reactions of chlorine

11.4.1
describe and interpret, in terms of changes in oxidation number, the reactions of chlorine with cold and with hot aqueous sodium hydroxide, and recognise them as disproportionation reactions
11.4.2
explain, including by use of an equation, the use of chlorine in water purification, to include the production of the active species HOCl and ClO⁻ which kill bacteria