Syllabus Edition

First teaching 2023

First exams 2025

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The Reactions of Chlorine (CIE A Level Chemistry)

Exam Questions

46 mins15 questions
11 mark

Chlorine is widely used in water treatment plants. Chlorine is reacted with water to produce hydrochloric acid and another chlorine-containing acid.

Which row correctly describes the properties of the reaction? 

 

Moles Cl2 used

Moles HCl produced

Other product formed

A

B

C

D

1

2

3

4

1

3

5

7

HClO

HClO2

HClO3

HClO4

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    21 mark

    When chlorine reacts with cold sodium hydroxide the following reaction occurs

    Cl2 (aq) + 2NaOH (aq) → NaCl (aq) + NaClO (aq) + H2O (l)

    Which of the following statements is correct?

    • The chlorine has only been oxidised 

    • The oxidation number of Cl in NaClO is 0

    • The chlorine is simultaneously oxidised and reduced 

    • The oxidation number of Cl in Cl2 is -1 

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    31 mark

    When chlorine reacts with hot sodium hydroxide the following reaction occurs.

    3Cl2 (g) + 6NaOH (aq) → 5NaCl (aq) + NaClO3 (aq) + 3H2O (l)

    Which row shows the correct oxidation state of chlorine in each ion?

     

    Cl2

    NaCl

    NaClO3

    A

    B

    C

    D

    0

    0

    0

    0

    -1

    +1

    +1

    -1

    +5

    -5

    -3

    +3

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      41 mark

      Chlorine is used to treat drinking water. 

      Which statement is correct?

      • Water reacts with chlorine to form hydrochloric acid and chloric(I) acid, HClO

      • When universal indicator is added to chloric(I) acid, HClO it turns blue then white

      • Chloric acid does not dissociate further when added to water

      • Chlorine reacts with cold sodium hydroxide to form sodium chloride and water only

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      11 mark

      When the yellow liquid NCl3 is stirred into aqueous sodium hydroxide, the reaction that occurs can be represented by the following equation.

      2NCl3 (l) + 6NaOH (aq) rightwards arrow N2 (g) + 3NaCl (aq) + 3NaClO (aq) + 3H2O (l)

      Which of the following is not correct for this reaction?

      • A bleaching solution remains after the reaction.

      • Effervescence will be observed.

      • The nitrogen is oxidised.

      • The final solution gives a precipitate with acidified silver nitrate.

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      21 mark

      Which is the correct equation for the reaction of hot, dilute aqueous sodium hydroxide, NaOH, and chlorine, Cl2?

      • Cl2 + 2NaOH → NaCl + NaClO + H2O

      • 1 halfCl2 + 2OH- → ClO- + H2O + e-

      • begin mathsize 16px style 1 half end styleCl2 + 6OH- → ClO3- + 3H2O + e-

      • 3Cl2 + 6NaOH → 3NaCl + 3NaClO3 + H2O

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      31 mark

      What is the main disinfectant formed when chlorine gas is added to water during purification?

      • HClO

      • HCl

      • ClO2 

      • CHCl3 

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      11 mark

      When chlorine is bubbled through aqueous sodium hydroxide solution different substances are formed depending on the conditions. Which statement is incorrect? 

      • In hot NaOH (aq), ClO3 (aq) ions are formed.

      • In cold NaOH (aq), ClO (aq) ions are formed.

      • The oxidation state of chlorine changes from 0 to +3

      • Disproportionation of chlorine occurs in both cold and hot aqueous solutions.

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      21 mark

      Which statement accurately describes the role of chlorine in the reaction with water?

      • Chlorine undergoes only oxidation in the reaction, resulting in the formation of ClO(aq)

      • Chlorine undergoes only reduction in the reaction, resulting in the formation of Cl (aq)

      • Chlorine undergoes both oxidation and reduction in the reaction, forming ClO (aq) and Cl (aq)

      • The oxidation state of chlorine changes from 0 to +5

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      31 mark

      A few drops of sodium chlorate (I) solution is added to potassium bromide solution. A red-brown gas is produced along with sodium chloride solution.

      Which of the following statements is correct?

      • The oxidation state of chlorine in NaClO is +5

      • Chlorine gas is produced

      • Bromide ions are oxidised in this reaction  

      • NaClO is the reducing agent 

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