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K326 / K328 / 2027
Qualitative Analysis

Chapter summary

Qualitative Analysis, at a glance

Identify ions and gases using observations that distinguish them.

O-Level 5086 / 5088 (2026) / SEC G3 K326 / K328 (2027)

Quick revision

Revisit the essentials, then return to an explanation when you need it.

For cations, record precipitate colour and behaviour in excess reagent. Use fresh portions. For chloride/sulfate tests acidify with nitric acid; do not introduce the ion being tested.

Check your understanding

Al3+ and Zn2+ both give white precipitates that dissolve in excess NaOH. Which reagent tells them apart?

  1. More NaOH, warmed: zinc's precipitate comes back, aluminium's stays dissolved.
  2. Aqueous ammonia: zinc's precipitate dissolves in excess, aluminium's does not.
  3. Silver nitrate, which gives a white precipitate with Al3+ but none with Zn2+.
Show the answer

Aqueous ammonia: zinc's precipitate dissolves in excess, aluminium's does not.

Use a fresh portion. Both give white precipitates with ammonia, but only zinc hydroxide dissolves in excess ammonia, giving a colourless solution.

Quick recall

Card 1 of 8. Answer in your head, then check.

Describe the test for hydrogen.

Revisit an explanation

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