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Analysis of Barium Bromide (BaBr₂)

Class 12 Chemistry Practical

How to do salt analysis · Viva · Quiz

Aim

To analyse the given inorganic salt for one acidic and one basic radical.

Preliminary Test

ExperimentObservationInference
Physical examinationWhite solid; odourlessNot copper / ammonium
SolubilitySoluble in waterSoluble barium halide
Flame testApple-green flameBa²⁺
Dilute H₂SO₄No CO₂; BaSO₄ may pptNot carbonate
Conc. H₂SO₄Reddish-brown vapours of Br₂Br⁻ may be present
Dry heatingNo brown NO₂ of nitrateNot Ba(NO₃)₂

Test of Anion (Br⁻)

ExperimentObservationInference
Heat the salt with conc. H₂SO₄Reddish-brown vapours of Br₂Br⁻ may be present
Confirmatory Tests
Layer test
To the aqueous extract add CCl₄ / CHCl₃ and chlorine water; shake		Orange-brown organic layerBr⁻ is confirmed
Silver nitrate
Acidify soda extract with dilute HNO₃ and add AgNO₃		Pale yellow ppt of AgBr, sparingly soluble in NH₄OHBr⁻ is confirmed

Ionic equations

  • 2Br⁻ + 2H₂SO₄ (conc.) → Br₂ ↑ + SO₂ + 2H₂O + SO₄²⁻
  • Ag⁺ + Br⁻ → AgBr ↓ (pale yellow)

Test of Cation (Ba²⁺)

ExperimentObservationInference
Groups I-IV reagents (dil. HCl, H₂S / acid, NH₄Cl + NH₄OH, H₂S / alkaline) give no pptNo precipitate in Groups I-IVGroups I-IV cations are absent
To the ammoniacal solution add (NH₄)₂CO₃White ppt of BaCO₃Group V may be present
Confirmatory Tests
Flame test
Flame test of the salt moistened with conc. HCl		Apple-green flameBa²⁺ is confirmed
Potassium chromate
Dissolve the carbonate ppt in acetic acid and add K₂CrO₄		Yellow ppt of BaCrO₄Ba²⁺ is confirmed

Ionic equations

  • Ba²⁺ + CrO₄²⁻ → BaCrO₄ ↓

Result

The given salt contains Ba²⁺ as the cation (basic radical) and Br⁻ as the anion (acidic radical). The salt is Barium Bromide (BaBr₂).

Precautions

  1. Use small quantities of salt and reagents; do not use excess.
  2. Keep the mouth of the test tube away from the face while heating.
  3. Use freshly prepared FeSO₄ for the brown ring test.
  4. Nessler’s reagent is toxic (mercury); handle with care and do not pipette by mouth.

Viva voce

  1. Why reddish-brown vapours?

    Bromine.

  2. Why layer test?

    Br₂ is more soluble in CCl₄ / CHCl₃ and colours the organic layer orange-brown.

  3. AgBr vs AgCl vs AgI?

    AgCl white, AgBr pale yellow, AgI yellow. AgCl readily soluble in NH₄OH; AgBr sparingly; AgI insoluble.

  4. Why apple-green?

    Barium flame.

  5. Why K₂CrO₄?

    Group V confirmatory for Ba²⁺.

  6. Why not chromyl chloride?

    That test is for chlorides, not bromides.

  7. Why not brown ring?

    Anion is bromide, not nitrate.

  8. Formula Ba(Br)₂?

    No. Write BaBr₂.

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