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The Halogens

Solid halides with concentrated sulfuric and phosphoric acid

  • 3 things to know
  • Unit AS 1

Overview

Recall questions on the equations and observations for sodium chloride, bromide and iodide with concentrated sulfuric acid, the reduction products of the acid in each case, the oxidation state changes of sulfur, what the series shows about the halide ions, and why phosphoric acid is used instead.

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 solid sodium chloride with concentrated sulfuric acid.

Key term

Describe what is observed when concentrated sulfuric acid is added to solid sodium chloride.

Key term

Why does solid sodium chloride give no redox reaction with concentrated sulfuric acid?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Write the equation for the reaction of solid sodium chloride with concentrated sulfuric acid.

    Model answer

    The equation is NaCl(s) + H₂SO₄(l) → NaHSO₄(s) + HCl(g).

  2. 2

    Describe what is observed when concentrated sulfuric acid is added to solid sodium chloride.

    Model answer

    Steamy white misty fumes of hydrogen chloride are given off, and the mixture effervesces.

  3. 3

    Why does solid sodium chloride give no redox reaction with concentrated sulfuric acid?

    Model answer

    The chloride ion is too weak a reducing agent to reduce the sulfur in sulfuric acid, so only an acid-base displacement of the hydrogen halide occurs.

  4. 4

    Name the products formed when concentrated sulfuric acid reacts with solid sodium bromide.

    Model answer

    Sodium hydrogensulfate, hydrogen bromide, bromine, sulfur dioxide and water are formed.

  5. 5

    Describe what is observed when concentrated sulfuric acid is added to solid sodium bromide.

    Model answer

    Steamy fumes of hydrogen bromide appear at first, followed by orange-brown fumes of bromine and a choking colourless gas.

  6. 6

    Write the equation showing bromide reducing concentrated sulfuric acid.

    Model answer

    The equation is 2HBr(g) + H₂SO₄(l) → Br₂(g) + SO₂(g) + 2H₂O(l).

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