Qualitative Analysis in the A-Level Inorganic Chemistry Curriculum

In A-level Chemistry, qualitative analysis usually focuses on identifying unknown ions and gases using standard laboratory tests, observational skills, and ionic equations. It is commonly taught within inorganic chemistry and practical or analytical chemistry sections of the course.

What the syllabus typically includes

1. Tests for common anions

  • Carbonate / hydrogencarbonate: acid added to produce carbon dioxide
  • Sulfate: acidified barium chloride gives a white precipitate
  • Halides (Cl-, Br-, I-): tested with silver nitrate and distinguished further with ammonia
  • Some specifications also include nitrate, nitrite, sulfite, and thiosulfate

2. Tests for common cations

  • Reaction with aqueous sodium hydroxide
  • Reaction with aqueous ammonia
  • Observation of precipitate colour, formation, and solubility in excess reagent
  • Common ions include NH4+ and transition-metal ions such as Cu2+, Fe2+, Fe3+, Cr3+, and Co2+

3. Gas tests

  • Ammonia: turns damp red litmus paper blue
  • Carbon dioxide: turns limewater milky
  • Hydrogen: squeaky pop with a lighted splint
  • Oxygen: relights a glowing splint

4. Practical identification of unknowns

  • Plan a sensible sequence of tests
  • Avoid misleading results caused by doing tests in the wrong order
  • Identify unknown salts or mixtures from observations
  • Write ionic equations and explain test results

How the main boards frame it

AQA

AQA places qualitative analysis mainly in its required practical work. Students are expected to carry out test-tube reactions to identify Group 2 and NH4+ cations, Group 7 halide ions, OH-, CO3^2-, SO4^2-, and transition-metal ions in aqueous solution.

OCR A

OCR places qualitative analysis in Module 3: Periodic table and energy. OCR materials indicate coverage of halides, sulfate, carbonate, ammonium, and transition-metal ion tests using sodium hydroxide and ammonia.

Pearson Edexcel

Edexcel explicitly includes tests for CO3^2- / HCO3-, SO4^2-, NH4+, halides, and the reactions of Cr3+, Fe2+, Fe3+, Co2+, and Cu2+ with aqueous sodium hydroxide and ammonia.

Cambridge International 9701

Cambridge provides detailed qualitative analysis notes covering reactions of cations, reactions of anions, tests for gases, and tests for elements. It explicitly expects familiarity with these standard tests.

Sources

Summary: qualitative analysis in A-level inorganic chemistry is mainly about identifying ions and gases using standard reagents, making accurate observations, and supporting conclusions with equations.