12.5.1

Testing Aqueous Cations 1

Test yourself

Metal Hydroxides

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.
Illustrative background for Zinc hydroxideIllustrative background for Zinc hydroxide ?? "content

Zinc hydroxide

  • Zinc ions (Zn2+) form the white precipitate zinc hydroxide.
    • The white precipitate dissolves in excess NaOH to give a colourless solution.

Jump to other topics

1States of Matter

2Atoms, Elements & Compounds

3Stoichometry

4Electrochemistry

5Chemical Energetics

6Chemical Reactions

7Acids, Bases & Salts

8The Periodic Table

9Metals

10Chemistry of the Environment

11Organic Chemistry

11.1Formulae, Functional Groups & Terminology

11.2Naming Organic Compounds

11.3Fuels

11.4Alkanes

11.5Alkenes

11.6Alcohols

11.7Carboxylic Acids

11.8Polymers

12Experimental Techniques & Chemical Analysis

Unlock your full potential with Seneca Premium

  • Unlimited access to 10,000+ open-ended exam questions

  • Mini-mock exams based on your study history

  • Unlock 800+ premium courses & e-books

Get started with Seneca Premium