8.3 Identification of Ions by Chemical & Spectroscopic Means

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Last updated 5:08 AM on 8/29/26
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20 Terms

1
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<p>Describe how to do a flame test.</p>

Describe how to do a flame test.

  • Pass nicrome wire through flame to sterilise it

  • Dip it into metal ion solution


2
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List all the positive metal ions used in the flame tests and their positive results.

  • Lithium (Li+) - crimson

  • Sodium (Na+) - yellow

  • Potassium (K+) - lilac

  • Calcium (Ca2+) - orange-red

  • Copper (Cu2+) - green


3
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If a sample contains a mixture of metal ions, a flame test may be inconclusive. Why?

Metal ion that is in highest conc. may mask others

4
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How do you perform the positive metal hydroxides tests?

  • Add sodium hydroxide to metal ion solution

  • Precipitate produced


5
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List all of the positive metal ions used in the sodium hydroxides tests and the coloured precipitate they produce.

  • Aluminum (Al3+) - white

  • Magnesium (Mg2+) - white

  • Calcium (Ca2+) - white

  • Copper (Cu2+) - blue

  • Iron (Fe2+) - green

  • Iron (Fe3+) - brown


6
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What is the half equation for the production of copper hydroxide?

Cu2+ + 2OH- → Cu(OH)2

7
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What is the half equation for the production of aluminium hydroxide?

Al3+ + 3OH- → Al(OH)3

8
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What is the half equation for the production of magnesium hydroxide?

Mg2+ + 2OH- → Mg(OH)2

9
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What is the half equation for the production of calcium hydroxide?

Ca2+ + 2OH- → Ca(OH)2

10
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What is the half equation for the production of iron (II) hydroxide?

Fe2+ + 2OH- → Fe(OH)2

11
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What is the half equation for the production of iron (III) hydroxide?

Fe3+ + 3OH- → Fe(OH)3

12
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When you add excess NaOH to an ____________ ion solution, the precipitate formed ___________.

  • aluminium

  • dissolves


13
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How do you perform the halides tests for negative metal ions?

  • Add dilute nitric acid + silver nitrate

    • precipitate produced


14
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Why can’t hydrochloric acid be used for the halide ion tests?

  • Contains chlorine

  • Would react + produce precipitate


15
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List the negative halide ions and the colour of the precipitate produced for the halide ion tests.

  • Bromine (Br-) - cream

  • Chlorine (Cl-) - white

  • Iodine (I-) - yellow


16
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How do you perform the test for sulfate ions?

  • Add hydrochloric acid + barium chloride

  • White precipitate


17
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Carbonates react with ________ _____ to form _______ _______ gas.

  • dilute acids

  • carbon dioxide


18
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What are 2 examples of instrumental methods?

  • Gas chromatography

  • Flame emission spectroscopy


19
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Why are instrumental methods better than chemical tests? (4)

They are:

  • sensitive

  • quantitative

  • accurate

  • rapid


20
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How do you perform flame emission spectroscopy?

  • Sample put into flame and light given out passed through spectroscope

  • Output is line spectrum — can be analysed to identify metal ions in solution + measure their concentrations