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CAIE A-Level Chemistry AS 11.4 The Reactions of Chlorine Questions

Practise chlorine disproportionation in alkali and the equations and active species involved in water purification.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Exam points

  • distinguish chloride plus chlorate(I) in cold dilute alkali from chloride plus chlorate(V) in hot alkali
  • track chlorine from oxidation number 0 to both −1 and +1 or +5 to demonstrate disproportionation
  • write chlorine hydrolysis in water and identify HClO or ClO− as the species that kills bacteria

Covered syllabus points

11.4.1—And interpret11.4.2—Explain

Question 1

[Maximum number: 1]

Chlorine gas is reacted with cold aqueous sodium hydroxide.
Which statement is correct for this reaction?

A

Chlorine is both oxidised and reduced.

B

Chlorine is neither oxidised nor reduced.

C

Chlorine is oxidised but not reduced.

D

Chlorine is reduced but not oxidised.

Question 2

[Maximum number: 1]

What is the oxidation state of the chlorine-containing species that kills bacteria in drinking water?

A

-1

B

+1

C

+3

D

+5

Question 3

[Maximum number: 1]

The equations for three reactions involving chlorine or its compounds are listed.

12KClO3→2KCl+3O224KClO3→3KClO4+KCl36KOH+3Cl2→3H2O+5KCl+KClO3\begin{array}{ll} 1 & 2 \mathrm{KClO}_{3} \rightarrow 2 \mathrm{KCl}+3 \mathrm{O}_{2} \\ 2 & 4 \mathrm{KClO}_{3} \rightarrow 3 \mathrm{KClO}_{4}+\mathrm{KCl} \\ 3 & 6 \mathrm{KOH}+3 \mathrm{Cl}_{2} \rightarrow 3 \mathrm{H}_{2} \mathrm{O}+5 \mathrm{KCl}+\mathrm{KClO}_{3} \end{array}

Which statement about these equations is correct?

A

Equation 1 describes the formation of a compound used to kill bacteria in drinking water.

B

Equation 1 does not represent a redox reaction.

C

Equation 2 describes the formation of potassium chlorate(IV).

D

Equations 2 and 3 both represent disproportionation reactions.

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