Qualitative Analysis for JEE Main 2026: Salt Analysis

Qualitative analysis (salt analysis) is tested in JEE Main as theory — you must know the characteristic reactions for identifying common cations and anions without actually performing them. The chapter rewards systematic memorisation of group reagents and confirmatory tests. This guide organises the information by analytical group, which is how to think about it in the exam.

Preliminary Tests

Before applying group reagents, perform preliminary tests: colour of salt (CuSO₄ is blue; FeSO₄ is green; K₂Cr₂O₇ is orange), smell (NH₄⁺ salts smell of ammonia on heating with NaOH; acetate smells of vinegar with H₂SO₄), flame test (Na⁺: persistent yellow; K⁺: lilac; Ba²⁺: apple green; Sr²⁺: crimson; Cu²⁺: blue-green). The flame test is the most immediately useful and should become reflexive. For the broader inorganic chemistry context see our inorganic memory tricks guide.

Cation Groups: Group Reagents and Precipitates

Group I (HCl reagent): Pb²⁺, Hg₂²⁺, Ag⁺ precipitate as white chlorides. Group II (H₂S in dilute HCl): Pb²⁺, Cu²⁺, Cd²⁺, Bi³⁺, As³⁺, Sb³⁺, Sn²⁺/⁴⁺ precipitate as sulphides. Group III (NH₄OH/NH₄Cl, then H₂S): Al³⁺, Fe³⁺, Cr³⁺ precipitate as hydroxides (no sulphide); then Ni²⁺, Co²⁺, Mn²⁺, Zn²⁺ as sulphides. Group IV (NH₄₂CO₃/NH₄OH): Ba²⁺, Sr²⁺, Ca²⁺ as carbonates. Group V (K₂CO₃): Mg²⁺ as white precipitate. Group VI: alkali metals (Na⁺, K⁺, NH₄⁺) — identified by flame test or special tests. Memorise the groups and their precipitate colours.

Confirmatory Tests for Common Cations

Fe²⁺: turns K₃[Fe(CN)₆] (potassium ferricyanide) blue (Turnbull's blue). Fe³⁺: turns K₄[Fe(CN)₆] (potassium ferrocyanide) blue (Prussian blue); turns SCN⁻ blood red. Cu²⁺: deep blue complex with excess NH₃ (tetraamminecopper(II)). Pb²⁺: K₂CrO₄ gives yellow PbCrO₄ precipitate. Ca²⁺: flame test (brick red) + CaC₂O₄ white precipitate with (NH₄)₂C₂O₄. Ba²⁺: flame test (apple green) + white BaSO₄ precipitate with H₂SO₄ (insoluble in HCl). These specific reagent-colour pairs are the confirmatory test facts most likely to appear in JEE.

Anion Groups and Identification

Dilute H₂SO₄ test: carbonate (CO₃²⁻) gives CO₂ (lime water turns milky); sulphite (SO₃²⁻) gives SO₂ (pungent, turns acidified K₂Cr₂O₇ green); nitrite (NO₂⁻) gives brown fumes of NO₂; acetate (CH₃COO⁻) gives smell of acetic acid; sulphide (S²⁻) gives H₂S (smell of rotten eggs). Concentrated H₂SO₄ test: chloride (Cl⁻) gives HCl (pungent, white fumes with NH₃); bromide (Br⁻) gives brown Br₂ fumes; iodide (I⁻) gives violet I₂ vapour; nitrate (NO₃⁻) gives brown ring test (FeSO₄ layer).

Special Confirmatory Tests for Anions

Carbonate: milky lime water + re-dissolves in excess CO₂. Sulphate: white BaSO₄ precipitate with BaCl₂ (insoluble in HCl — distinguishes from BaSO₃). Nitrate (brown ring test): freshly prepared FeSO₄ solution layered with conc. H₂SO₄ — brown ring of [Fe(NO)(H₂O)₅]²⁺ at interface. Phosphate: ammonium molybdate test — yellow precipitate of ammonium phosphomolybdate. Bromide: Cl₂ water + CCl₄ — orange-brown CCl₄ layer. Iodide: Cl₂ water + CCl₄ — violet CCl₄ layer. These confirmatory tests and their characteristic colours are a direct JEE memorisation task. After reviewing all salt analysis procedures, take a free mock test.