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Combined Science Chemistry

Chemistry study notes

Qualitative Analysis

Identify ions and gases using observations that distinguish them.

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

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4 topics

  1. Distinguish aqueous cations

    Observe a few drops first, then add the reagent in excess.

  2. Identify anions with the correct reagents

    Acidification matters because contaminants can imitate the result.

  3. Identify the gas, not just the bubbles

    A named gas needs a specific test and observation.

  4. Turn observations into a justified conclusion

    Use independent evidence and distinguish uncertainty from absence.

Scope and references

Learning outcomes and sources

6. Qualitative Analysis (5086 / 5088 / K326 / K328). Use the outcome map to find the explanation for a particular syllabus requirement.

See the learning outcome map

  1. 6(a) Identify aqueous cations

    • NaOH and/or ammonia; precipitate formation and excess solubility
    • Al3+, NH4+, Ca2+, Cu2+, Fe2+, Fe3+, Zn2+
    • Ammonium warming and evolved gas
    • Complex-ion formulae not required

    Distinguish aqueous cationsTurn observations into a justified conclusion

  2. 6(b) Identify anions

    • Carbonate with dilute acid and limewater
    • Chloride with nitric acid and silver nitrate
    • Nitrate with aluminium/NaOH, warming and damp red litmus
    • Sulfate with nitric acid and barium nitrate

    Identify anions with the correct reagentsTurn observations into a justified conclusion

  3. 6(c) Identify gases

    • NH3 damp red litmus
    • CO2 limewater
    • Cl2 damp litmus
    • H2 lighted splint
    • O2 glowing splint
    • SO2 acidified manganate(VII)

    Identify the gas, not just the bubbles