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The Halogens

Disproportionation of the halogens with sodium hydroxide

  • 3 things to know
  • Unit AS 1

Overview

Commercial use of sodium chlorate(V) and why chlorate(I) is a stronger oxidising agent than chloride.

What you need to know

Answer each one before you reveal it.

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Key term

Write the equation for the reaction of chlorine with cold dilute aqueous sodium hydroxide.

Key term

Name the two sodium salts formed when chlorine reacts with cold dilute sodium hydroxide.

Key term

Give the oxidation states of chlorine in the two products of its reaction with cold dilute sodium hydroxide

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Write the equation for the reaction of chlorine with cold dilute aqueous sodium hydroxide.

    Model answer

    The equation is Cl₂(g) + 2NaOH(aq) → NaCl(aq) + NaClO(aq) + H₂O(l).

  2. 2

    Name the two sodium salts formed when chlorine reacts with cold dilute sodium hydroxide.

    Model answer

    Sodium chloride and sodium chlorate(I) are formed.

  3. 3

    Give the oxidation states of chlorine in the two products of the cold dilute reaction.

    Model answer

    Chlorine is −1 in the chloride and +1 in the chlorate(I).

  4. 4

    Explain why the reaction of chlorine with cold dilute sodium hydroxide is a disproportionation.

    Model answer

    The chlorine begins at oxidation state 0 and ends at both −1 and +1, so the same element is simultaneously reduced and oxidised.

  5. 5

    State the common commercial use of the mixture formed when chlorine reacts with cold dilute sodium hydroxide.

    Model answer

    The mixture is sold as household bleach, because the chlorate(I) ion is a powerful oxidising agent.

  6. 6

    Write the equation for the reaction of chlorine with hot concentrated aqueous sodium hydroxide.

    Model answer

    The equation is 3Cl₂(g) + 6NaOH(aq) → 5NaCl(aq) + NaClO₃(aq) + 3H₂O(l).

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