Salt Analysis for JEE Main: Complete Guide

Salt Analysis (Qualitative Inorganic Analysis) is a chapter that many JEE Main aspirants underestimate, yet it contributes 1–2 questions per session and is a reliable source of easy marks for well-prepared students. The chapter tests knowledge of characteristic colour precipitates, confirmatory tests for specific ions, group separations, and the chemical reasoning behind each test. Unlike many chemistry chapters that require calculation, salt analysis is almost entirely qualitative and conceptual — making it an excellent chapter for students looking to add easy marks without heavy calculation burden.

Preliminary Tests and Characteristic Colours

Before formal analysis, preliminary observations give immediate information: (1) Colour of salt — CuSO4·5H2O is blue; FeSO4·7H2O is pale green; K2Cr2O7 is orange; KMnO4 is purple; CoCl2 is pink; NiSO4 is green; MnSO4 is light pink. (2) Smell — NH4+ salts give ammonia smell on heating with NaOH. (3) Action of heat — carbonate and bicarbonate salts give CO2 (turns lime water milky); nitrate salts give O2 + brown NO2 fumes (brown ring test). (4) Wet chemical reaction — add dilute H2SO4: CO2 gas (carbonates), SO2 gas (sulphites), H2S gas (sulphides), HCl/HBr/HI (halides — each with characteristic smell and confirmatory tests). These preliminary tests narrow the possibilities significantly before formal group analysis. For the broader inorganic chemistry context and group chemistry, see our p-Block Elements Guide.

Flame test for cations: Li (crimson red), Na (golden yellow), K (violet — seen through blue glass), Ca (brick red), Ba (apple green), Sr (carmine/scarlet), Cu (blue-green). The flame colours are tested directly in JEE Main — "which element gives a golden yellow flame test?" (Na). Yellow colour with blue cobalt glass test: Ba gives green → confirms barium vs. calcium (calcium gives red in cobalt glass too, but different shade).

Cation Analysis: Group Precipitation

Group 0 (NH4+): Add NaOH, warm — pungent smell of NH3, turns moist red litmus blue. Group 1 (Ag+, Pb2+, Hg2²+): precipitated by dilute HCl as white chloride precipitates (AgCl, PbCl2, Hg2Cl2). PbCl2 is soluble in hot water (distinguish from others). AgCl dissolves in NH3 (soluble in ammonia), Hg2Cl2 turns black with NH3. Group 2 (HgS, PbS, Bi2S3, CuS, CdS, As2S3, Sb2S3, SnS2): precipitated by H2S in acidic medium. Colours: CuS (black), PbS (black), CdS (yellow), As2S3 (yellow), HgS (black), SnS2 (yellow). Group 3 (Fe3+, Al3+, Cr3+): precipitated by NH4OH + NH4Cl. Fe(OH)3 (brown), Al(OH)3 (white gelatinous), Cr(OH)3 (green). Group 4 (Co2+, Ni2+, Mn2+, Zn2+): precipitated by H2S in alkaline medium (NH3/NH4Cl). CoS (black), NiS (black), MnS (flesh coloured/salmon pink), ZnS (white). Group 5 (Ca2+, Sr2+, Ba2+): precipitated by (NH4)2CO3. Group 6 (Mg2+): precipitated by Na2HPO4 + NH4OH → white precipitate of Mg(NH4)PO4. Practise salt analysis identification questions on our JEE Main chemistry mock tests with answer explanations for each group reaction.

Confirmatory tests for key cations: Cu2+ — deep blue colour with excess NH3 (tetrammine copper(II)); Fe3+ — blood red colour with KSCN/NH4SCN; Fe2+ — Prussian blue precipitate with K3[Fe(CN)6]; Co2+ — blue colour with KNO2 in acetic acid (K3[Co(NO2)6] precipitation). These specific colour reactions are high-frequency JEE Main questions.

Anion Analysis: Confirmatory Tests

Anion analysis uses dilute H2SO4, concentrated H2SO4, and specific reagents. CO3²- and HCO3-: CO2 with dilute H2SO4 — turns lime water milky (Ca(OH)2 + CO2 → CaCO3). Distinguish HCO3- from CO3²-: HCO3- gives CO2 with dilute H2SO4 at room temperature; CO3²- also does. Add MgCl2 to solution — CO3²- gives white precipitate (MgCO3), HCO3- does not precipitate. SO4²-: add BaCl2 — white precipitate of BaSO4, insoluble in dilute HCl. SO3²-: add dilute H2SO4 — SO2 gas (pungent smell); add K2Cr2O7 solution — turns green (Cr3+). Cl-: add dilute H2SO4 + AgNO3 — white curdy precipitate of AgCl, soluble in NH3. Br-: add AgNO3 — pale yellow precipitate of AgBr, sparingly soluble in NH3. I-: add AgNO3 — yellow precipitate of AgI, insoluble in NH3. NO3-: brown ring test — layer FeSO4 solution under concentrated H2SO4 — brown ring at interface: [Fe(NO)]²+. NO2-: turns starch-iodide paper blue (oxidises I- to I2).

Distinguish between SO3²- and SO4²- (common confusion): SO3²- gives SO2 with dilute H2SO4 while SO4²- does not. Both give white precipitate with BaCl2 but BaSO3 dissolves in dilute HCl while BaSO4 does not. This chemical distinction is a direct JEE Main question type. Similarly, distinguish Cl- from Br- from I-: colour of precipitate with AgNO3 (white, pale yellow, yellow) and solubility in NH3 (soluble, sparingly soluble, insoluble).

Common JEE Main Salt Analysis Question Types

JEE Main tests salt analysis through: (1) Multiple correct-type questions identifying ions based on a combination of observations. (2) Single correct questions asking which reagent distinguishes between two given ions. (3) Statement-based questions testing whether a specific chemical reaction in qualitative analysis is correctly described. (4) Structural/conceptual questions on the chemistry behind a test (e.g., why does FeSO4 form a brown ring with NO3- and concentrated H2SO4?). For type (4): concentrated H2SO4 reduces NO3- to NO, which then reacts with Fe2+ to form the brown [Fe(NO)]SO4 complex. Understanding the chemistry makes the test memorable rather than requiring rote memorisation. Sign up on our platform for salt analysis practice tests with visual precipitate colour guides. Our premium subscription includes access to all JEE Main inorganic chemistry question banks. For group chemistry that complements salt analysis, our d and f Block Elements Guide covers transition metal chemistry relevant to Group 2, 3, and 4 cation analysis.

Exam tip: salt analysis questions in JEE Main are typically scenario-based — "a salt gives X with reagent A and Y with reagent B — identify the cation and anion." Practise these scenario questions rather than isolated single-reagent recall. A systematic elimination approach (start with colour, then flame test, then group separation) is faster than trying to match all observations simultaneously.