chem salts

Systematic Qualitative Analysis of Simple Inorganic Salts

  • Definition: Identification of cations and anions in salts formed by neutralization of an acid and base.

  • Charges and Valency: The number of units of charge carried by an ion equals its valency.

Classification of Radicals

Acid Radicals (Anions)

  • Carry a negative charge (-)

  • Detection:

    • Tested using solid salt (0.1g)

    • Detected in acidic medium (pH < 7)

    • Reactions visible as effervescence, color, or odor of gas.

Basic Radicals (Cations)

  • Carry a positive charge (+)

  • Detection:

    • Detected using original solution (2-3 drops)

    • Detected in basic medium (pH > 7)

    • Reactions observed as precipitates.

Steps in Salt Analysis

  1. Preliminary Test:

    • Determine state: Crystalline or Amorphous

    • Observe color: (e.g., light green for Fe, blue for Cu).

    • Solubility Tests: Test in water, dil. HCl, and dil. HNO3 at different temperatures.

  2. Identification of Anions (Acid Radicals):

    • Group I: Use diluted H2SO4/diluted HCl to detect CO₃²⁻.

    • Group II: Use concentrated H2SO4 for Cl⁻, Br⁻, NO₃⁻.

    • Group III: No reagents required for SO₄²⁻.

  3. Detection of Cations (Basic Radicals):

    • Prepare original solution (OS) using water or HCl based on solubility tests.

    • Use reagents to confirm the presence of specific cations (Al³⁺, Zn²⁺, etc.).

Confirmatory Tests for Anions

Carbonate Anion (CO₃²⁻)

  • Experiment: Add diluted H2SO4; observe effervescence releasing CO₂.

  • Lime Water Test: If CO₂ passes into lime water, it turns milky.

Chloride Anion (Cl⁻)

  • Silver Nitrate Test:

    • Observation: Curdy white precipitate forms, soluble in excess NH₄OH.

    • Chromyl Chloride Test: Produces orange-red vapors and a yellow solution when NaOH is added.

Bromide Anion (Br⁻)

  • Tests yield reddish brown fumes, indicating presence.

Nitrate Anion (NO₃⁻)

  • Brown Ring Test: Formation of a brown ring confirms presence.

Sulfate Anion (SO₄²⁻)

  • BaCl₂ Test: A thick white precipitate confirms sulfate presence.

Detection of Cations (Basic Radicals)

  • Preparation of Original Solution (OS):

    • Salt dissolved in appropriate solvent, and saturated solution obtained.

Cation Groups and Tests

  • Group I:

    • Ammonium Ion (NH₄⁺): Pungent smell, gives white fumes with HCl.

  • Group II Cations: Confirmed by the absence of precipitates.

  • Group III Cations (Al³⁺):

    • Test: Use excess NH₄OH to produce a gelatinous white precipitate.

  • Group IV Cations (Zn²⁺, Mn²⁺):

    • Tests for zinc and manganese confirm their presence based on coloration and reactions.

  • Group V Cations (Ba²⁺, Sr²⁺, Ca²⁺): Flame tests provide characteristic colors confirming these ions.

Preparation of Nessler's Reagent

  • Components: Potassium mercuric iodide solution formed from HgCl₂ and KI.

    • Procedure: Adding KI to HgCl₂ forms a red precipitate which dissolves in excess KI giving clear solution.

A brief explanation is a concise summary or clarification of a particular topic or concept. It provides essential information without unnecessary detail, making it easier for readers to grasp the main points quickly. Brief explanations are commonly used in educational contexts, professional environments, and everyday communication to convey ideas efficiently.