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Periodicity and Group Chemistry

Tests for Ammonium, Group 2, Hydroxide and Carbonate Ions

  • 3 things to know
  • Papers 1 and 3

Overview

The reagents, observations and equations for each of these tests.

What you need to know

Answer each one before you reveal it.

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Key term

Why is the test for sulfate ions carried out before the test for halide ions?

Key term

What reagent is added, and what is done, to test a solution for ammonium ions?

Key term

What gas is released when sodium hydroxide is warmed with a solution containing ammonium ions?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What reagent is added, and what is done, to test a solution for ammonium ions?

    Model answer

    Sodium hydroxide solution is added and the mixture is warmed gently.

  2. 2

    What gas is released when sodium hydroxide is warmed with a solution containing ammonium ions?

    Model answer

    Ammonia gas (NH₃).

  3. 3

    Write the ionic equation for the reaction that releases ammonia in the test for ammonium ions.

    Model answer

    NH₄⁺ + OH⁻ → NH₃ + H₂O.

  4. 4

    How is the gas produced in the ammonium ion test identified?

    Model answer

    It turns damp red litmus paper blue (ammonia is alkaline) and has a pungent smell.

  5. 5

    Why is the mixture warmed when testing for ammonium ions?

    Model answer

    Warming drives the ammonia gas out of solution so it can reach and turn the damp red litmus paper blue.

  6. 6

    What reagent is used to identify Group 2 cations in a simple test-tube reaction?

    Model answer

    Sodium hydroxide solution.

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