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Qualitative Tests

Chemical tests for the gases

  • 3 things to know
  • Unit AS 1

Overview

Test for hydrogen gas and the result, test for oxygen gas and the result and test for chlorine gas and the result.

What you need to know

Answer each one before you reveal it.

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Key term

Describe the test and the result for hydrogen, oxygen, chlorine and carbon dioxide.

Key term

Why does chlorine both redden and bleach damp litmus paper?

Key term

Describe the test for hydrogen gas and the result.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Describe the test for hydrogen gas and the result.

    Model answer

    A lighted splint is held at the mouth of the tube and the gas burns with a squeaky pop.

  2. 2

    Describe the test for oxygen gas and the result.

    Model answer

    A glowing splint is held in the gas and it relights.

  3. 3

    Describe the test for chlorine gas and the result.

    Model answer

    Damp blue litmus paper is held in the gas, and it turns red and is then bleached white.

  4. 4

    Why does chlorine both redden and bleach damp litmus paper?

    Model answer

    Chlorine reacts with the water on the paper to give an acidic solution, which reddens the litmus, and the chlorate(I) formed then oxidises the dye and removes the colour.

  5. 5

    Describe the test for carbon dioxide and the result.

    Model answer

    The gas is bubbled through limewater, which turns milky.

  6. 6

    Write the equation for the reaction of carbon dioxide with limewater.

    Model answer

    The equation is Ca(OH)₂(aq) + CO₂(g) → CaCO₃(s) + H₂O(l).

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