8.3.3

Metal Hydroxides

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Metal Hydroxides - Calcium, Magnesium and Aluminium

Metal ions can be found in aqueous solutions of metal compounds. These ions can precipitate out of solution when they react with a sodium hydroxide solution (NaOH). This produces insoluble solids (don't dissolve in water) called precipitates.

Illustrative background for Calcium hydroxideIllustrative background for Calcium hydroxide ?? "content

Calcium hydroxide

  • Calcium ions (Ca2+) form the white precipitate calcium hydroxide.
    • Ca2+(aq) + 2OH-(aq) → Ca(OH)2(s)
Illustrative background for Magnesium hydroxideIllustrative background for Magnesium hydroxide ?? "content

Magnesium hydroxide

  • Magnesium ions (Mg2+) form the white precipitate magnesium hydroxide.
    • Mg2+(aq) + 2OH-(aq) → Mg(OH)2(s)
Illustrative background for Aluminium hydroxideIllustrative background for Aluminium hydroxide ?? "content

Aluminium hydroxide

  • Aluminium ions (Al3+) form the white precipitate aluminium hydroxide.
    • Al3+(aq) + 3OH-(aq) → Al(OH)3(s)
  • Unlike the other two white precipitates, aluminium hydroxide can be dissolved in excess NaOH. This produces a colourless solution.

Metal Hydroxides - Copper, Iron(II) and Iron (III)

Here are some more examples of the formation of precipitates:

Illustrative background for Copper(II) hydroxideIllustrative background for Copper(II) hydroxide ?? "content

Copper(II) hydroxide

  • Copper ions (Cu2+) form the blue precipitate copper(II) hydroxide.
    • Cu2+(aq) + 2OH-(aq) → Cu(OH)2(s)
Illustrative background for Iron(II) hydroxideIllustrative background for Iron(II) hydroxide ?? "content

Iron(II) hydroxide

  • Iron(II) ions (Fe2+) form the green precipitate iron(II) hydroxide.
    • Fe2+(aq) + 2OH-(aq) → Fe(OH)2(s)
Illustrative background for Iron(III) hydroxideIllustrative background for Iron(III) hydroxide ?? "content

Iron(III) hydroxide

  • Iron(III) ions (Fe3+) form the brown precipitate iron(III) hydroxide.
    • Fe3+(aq) + 3OH-(aq) → Fe(OH)3(s)

Jump to other topics

1Atomic Structure

2Chemical Bonding

3Quantitative Chemistry

4Chemical Changes

5Energy Changes

6The Rate & Extent of Chemical Change

7Organic Chemistry

8Chemical Analysis

9Chemistry of the Atmosphere

10Using Resources

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