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Testing for Carbonate and Halides

There is a specific way to test for the presence of carbonates and halides.

Testing for carbonates

Testing for carbonates

  • Carbonates are compounds containing CO32− ions.
  • Carbonates react with dilute acids to form a salt, carbon dioxide, and water.
    • E.g. calcium carbonate + hydrochloric acid → calcium chloride + carbon dioxide + water
Testing for carbonates cont.

Testing for carbonates cont.

  • As carbon dioxide is produced, we can use the standard carbon dioxide test to work out if an unknown substance is a carbonate.
    • This test involves bubbling the gas through limewater. If the solution turns cloudy, the gas is carbon dioxide and the compound is a carbonate.
Testing for halides

Testing for halides

  • Halides are compounds containing ions of halogen atoms.
  • There are two steps to halide testing:
    • Add dilute nitric acid to an unknown solution.
      • This removes carbonate ions. These could disrupt test results by forming a precipitate with the silver ions added in the second step.
    • Add silver nitrate to the same solution.
      • If halide ions are present, they will form a precipitate with the silver ions.
Testing for halides cont.

Testing for halides cont.

  • Ag+(aq) + Cl-(aq) → AgCl(s)
    • Silver chloride is white.
  • Ag+(aq) + Br-(aq) → AgBr(s)
    • Silver bromide is cream.
  • Ag+(aq) + I-(aq) → AgI(s)
    • Silver iodide is pale yellow.
Jump to other topics
1

Atomic Structure

2

Chemical Bonding

3

Quantitative Chemistry

4

Chemical Changes

5

Energy Changes

6

The Rate & Extent of Chemical Change

7

Organic Chemistry

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Chemical Analysis

9

Chemistry of the Atmosphere

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Using Resources

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