ICSE Class 10 Chemistry: Analytical Chemistry — Notes 2026

Introduction to Analytical Chemistry

• Branch of chemistry concerned with identifying and quantifying chemical species
• Qualitative analysis: what is present; quantitative analysis: how much is present
• Systematic approach: preliminary tests → tests in solution → confirmatory tests

Preliminary Tests (Dry Tests)

• Colour of salt: Cu²⁺ (blue-green), Fe³⁺ (yellow-brown), Fe²⁺ (pale green), Co²⁺ (pink)
• Flame test: Na⁺ (yellow), K⁺ (lilac), Ca²⁺ (brick red), Cu²⁺ (blue-green), Sr²⁺ (crimson)
• Action of heat: decomposition, colour change, gas evolved

Action of Dilute H₂SO₄

• CO₃²⁻ → CO₂ (turns lime water milky)
• S²⁻ → H₂S (rotten egg smell, turns lead acetate paper black)
• NO₂⁻ → brown fumes of NO₂; SO₃²⁻ → SO₂ (smell of burning sulfur)

Tests in Solution — Cations

• NH₄⁺: warm with NaOH → NH₃ (pungent, turns red litmus blue)
• Fe³⁺: add NaOH → red-brown precipitate; add KSCN → blood-red colour
• Cu²⁺: add NaOH → blue ppt; add excess NH₃ → deep blue solution (tetraammine)

Tests in Solution — Anions

• Cl⁻: AgNO₃ → white precipitate (AgCl) soluble in NH₃
• Br⁻: AgNO₃ → pale yellow ppt (AgBr) sparingly soluble in NH₃
• I⁻: AgNO₃ → yellow ppt (AgI) insoluble in NH₃; starch-iodide turns blue

Confirmatory Tests

• Confirm Pb²⁺: H₂S gas → black PbS ppt; K₂CrO₄ → yellow PbCrO₄ ppt
• Confirm SO₄²⁻: add HCl first (remove CO₃²⁻), then BaCl₂ → white BaSO₄ ppt
• Confirm NO₃⁻: brown ring test — Fe²⁺ + NO₃⁻ + H₂SO₄ → brown ring at interface

ICSE Exam Tips — Salt Analysis

• Always state observations clearly: colour, smell, precipitate
• Follow sequence: never add confirmatory reagent without preliminary test result
• Common error: not acidifying before BaCl₂ test for sulfate