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Analysis of Barium Chloride (BaCl₂)

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 crystalline solid; odourlessNot ammonium / acetate / copper
SolubilitySoluble in waterBaCl₂ is soluble; BaSO₄ / BaCO₃ are not
Dry heatingNo sublimation; no brown fumesNot NH₄Cl / lead nitrate
Flame testApple-green flameBa²⁺ indicated
Dilute H₂SO₄No CO₂; a white ppt of BaSO₄ may formNot carbonate; sulphate from the acid
Conc. H₂SO₄Colourless HCl gas; white fumes with NH₄OHCl⁻ may be present

Test of Anion (Cl⁻)

ExperimentObservationInference
Heat a pinch of salt with conc. H₂SO₄Colourless gas with a pungent smell; dense white fumes with NH₄OHCl⁻ may be present
Confirmatory Tests
MnO₂ / conc. H₂SO₄
Heat the salt with conc. H₂SO₄ and a pinch of MnO₂		Greenish-yellow chlorine gas is evolvedCl⁻ is indicated
Silver nitrate
Acidify the soda extract with dilute HNO₃ and add AgNO₃, then NH₄OH		Curdy white ppt of AgCl, soluble in NH₄OH, reappears with dilute HNO₃Cl⁻ is confirmed
Chromyl chloride
Heat salt + K₂Cr₂O₇ + conc. H₂SO₄. Pass vapours into NaOH; acidify with acetic acid and add lead acetate		Yellow chromyl chloride vapours; yellow ppt of PbCrO₄Cl⁻ is confirmed (chromyl chloride test)

Ionic equations

  • NaCl + H₂SO₄ (conc.) → NaHSO₄ + HCl ↑
  • MnO₂ + 4HCl → MnCl₂ + Cl₂ ↑ + 2H₂O
  • Ag⁺ + Cl⁻ → AgCl ↓ (white)
  • AgCl + 2NH₄OH → [Ag(NH₃)₂]Cl + 2H₂O

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⁺ + CO₃²⁻ → BaCO₃ ↓
  • Ba²⁺ + CrO₄²⁻ → BaCrO₄ ↓ (yellow)

Result

The given salt contains Ba²⁺ as the cation (basic radical) and Cl⁻ as the anion (acidic radical). The salt is Barium Chloride (BaCl₂).

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 apple-green flame?

    Characteristic atomic emission of barium.

  2. Why is the wire cleaned with conc. HCl?

    To convert the salt to volatile chloride and remove traces of previous salts.

  3. Why Group V after I-IV are absent?

    Otherwise carbonates of earlier groups would also ppt with (NH₄)₂CO₃.

  4. Why acetic acid before K₂CrO₄?

    BaCrO₄ ppts in acetic acid. SrCrO₄ does that less readily, which helps tell Ba from Sr.

  5. Why AgNO₃ for the anion?

    Cl⁻ gives curdy white AgCl soluble in NH₄OH.

  6. Why is BaCl₂ used as a reagent for sulphate?

    Because BaSO₄ is extremely insoluble. Same cation plus sulphate.

  7. Why no Nessler?

    Cation is Ba²⁺, not NH₄⁺.

  8. Why dilute H₂SO₄ can confuse?

    It precipitates BaSO₄ from a soluble barium salt. That is not a carbonate test.

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