IP Chemistry Upper Sec 06: Qualitative Analysis

Study guide26 Nov 2025, 00:00 ZUpdated 30 Nov 2025

Systematic tests for common cations, anions, and gases for IP Sec 3-4 Chemistry (O-Level 6092, 2026).

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These notes align with SEAB GCE O-Level Chemistry (6092) content used in IP programmes (exams from 2026).

Status: SEAB O-Level Chemistry 6092 syllabus (exams from 2026) checked 2025-11-30 - scope unchanged; remains the reference for this note.

The core idea is simple: Qualitative analysis is a controlled sequence of tests and observations.

Use it as a working check: Use fresh samples, test gases first, then cations, then anions. Record colour, precipitate formation, and solubility in excess reagent.

Then go one layer deeper: Example: a blue precipitate that dissolves in excess ammonia to form a deep blue solution points to copper ions. Vague wording like "colour changed" loses marks.

If you need the O-Level QA table

This IP note teaches the decision sequence. For the exam-facing 6092 table route, use the dedicated O-Level Chemistry QA table toolkit.

Search intent	Best route
`qa table`, `o level qa table`, or `qa notes o level`	Use the O-Level QA toolkit and verify against the official 6092 Notes for Qualitative Analysis.
`qualitative analysis notes` for IP Sec 3 or Sec 4	Stay on this note for sequence, observation wording, and lookalike traps.
`in excess qa`	Use the in-excess QA mark-trap guide after you know the cation test result.

What you must know

Gas tests: $\ce{H2}$

Reviewed by

Azmi·Senior Chemistry Specialist

Sources

SEAB GCE O-Level Chemistry (6092) syllabus (examinations from 2026)

First clue	Next test	What conclusion needs
Gas forms when acid is added.	Test the gas immediately with limewater, damp litmus, or acidified $\ce{KMnO4}$ .	Name the gas and the ion source, such as carbonate producing $\ce{CO2}$ .
A precipitate forms with NaOH.	Add excess NaOH, then repeat with aqueous ammonia on a fresh sample.	Colour first, then whether the precipitate dissolves in excess reagent.
No obvious cation clue appears.	Move to anion tests on fresh portions after acidifying where required.	State the acidified reagent and the precipitate colour.
Two ions seem possible from the same observation.	Add a confirmatory test rather than guessing.	A second result that separates the lookalikes, such as $\ce{Zn^{2+}}$ dissolving in excess ammonia while $\ce{Al^{3+}}$

First result	Excess NaOH result	Aqueous ammonia result	What to do next
White ppt with NaOH	Dissolves in excess NaOH	Does not dissolve in excess ammonia	Suspect $\ce{Al^{3+}}$ within the 6092 QA table.
White ppt with NaOH	Dissolves in excess NaOH	Dissolves in excess ammonia	Identify $\ce{Zn^{2+}}$ . The ammonia result separates zinc from aluminium.
White ppt with NaOH	Insoluble in excess NaOH	Insoluble in excess ammonia	Suspect $\ce{Ca^{2+}}$ if the rest of the data fits; check against flame test or other given clues.

First observation or target	Next reagent or test	Conclusion you can make	Common trap
Effervescence when dilute acid is added	Bubble the gas through limewater	Milky limewater supports $\ce{CO3^{2-}}$ because $\ce{CO2}$ was produced	Writing "carbonate" from bubbles alone without testing the gas
Choking gas from acidified sample	Test with acidified $\ce{KMnO4}$ only when instructed	Purple solution decolourises if $\ce{SO2}$
Test for sulfate	Acidify with dilute nitric acid, then add aqueous barium nitrate	White precipitate after acidification supports $\ce{SO4^{2-}}$	Skipping acidification and letting carbonate form a false white precipitate
Test for halide	Acidify with dilute nitric acid, then add $\ce{AgNO3}$	White or yellow precipitate points to chloride or iodide in 6092	Using the same sample that already received barium reagent
Test for nitrate	Warm with aqueous $\ce{NaOH}$ and aluminium foil	Ammonia gas supports $\ce{NO3-}$

Test situation	Observation sentence to write	Inference sentence to write	Common trap
NaOH is added dropwise, then in excess	"A blue precipitate forms and remains insoluble in excess sodium hydroxide."	"This result is consistent with copper(II) ions, but check the aqueous ammonia result too."	Writing only "copper(II) is present" without colour or excess result
Aqueous ammonia is added dropwise, then in excess	"A blue precipitate forms and dissolves in excess aqueous ammonia to give a deep blue solution."	"This confirms copper(II) ions when paired with the NaOH result."	Saying "solution turns blue" and missing the precipitate step
A gas is produced on warming with sodium hydroxide	"A pungent gas is produced and turns damp red litmus paper blue."	"The gas is ammonia, so ammonium ions are present."	Naming ammonium ions before proving the gas is ammonia
Acidified silver nitrate gives a precipitate	"A white precipitate forms after acidifying and adding silver nitrate."	"This supports chloride ions."	Omitting the acidification step or writing only "halide present"

IP Chemistry Upper Sec 06: Qualitative Analysis

If you need the O-Level QA table

What you must know

Sources

Observation-to-test checkpoint

White precipitate cation checkpoint

Gas and anion sequence checkpoint

Observation wording checkpoint

Detailed notes

Worked walkthroughs

Pitfalls and fixes

Practice drills

Quick applications

Exam cues

Next steps

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