Testing for negative Ions

Struggling to understand which ions have what added to them, and what happens to the ions, heres some quick and easy flash cards to help you :)

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Introduction

There are 4 main tests for negative ions which you need to know for the exam:

  • Carbonate Ions
  • Halide Ions
  • Sulfate Ions
  • Nitrate ions
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Carbonate and Halide Ions

To test for carbonate ions we:

Add dilute Hydrochloric acid (HCL) to the substance to see if it fizzes.

If it does fizz and the gas produced turns lime water cloudy, the substance contains carbonate ions


To test for Halide ions we:

Add dilute Nitric acid and then silver nitrate solution to the substance.

  • Chloride Ions produce a white precipitate
  • Bromide ions produce a cream precipitate
  • Iodide ions produce a yellow precipitate

Notice the ions get darker in order going down their group in the periodic table

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Sulfate and Nitrate Ions

The test for Sulfate ions:

  • Add dilute hydrochloric acid (HCL) and them Barium chloride solution to the substance
  • If a WHITE precipitate forms, sulfate ions are present

The test for Nitrate ions:

  • Add some Aluminum powder and then some sodium hydroxide solution to the substance.
  • Gently warm and test the gas given off with damp red litmus paper
  • If the paper turns blue, ammonia was produced and Nitrate ions are present
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Decomposing tests

Carbonate produce carbon dioxide (co²) when they decompose (breaking down using heat)

  • Copper carbonate is green but turns to a black copper oxide when heated
  • Zinc oxide is white, and turns yellow when heated, but it cools back to a white colour



Hope this helped :D

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