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Analysis of Strontium Chloride (SrCl₂)

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 chloride
Flame testCrimson-red flameSr²⁺ indicated
Dilute H₂SO₄No CO₂; SrSO₄ may slowly pptNot carbonate
Conc. H₂SO₄HCl gas; white fumes with NH₄OHCl⁻ may be present
Dry heatingNo brown fumes / sublimationNot nitrate / NH₄Cl

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 (Sr²⁺)

ExperimentObservationInference
Groups I-IV reagents give no ppt. Then add (NH₄)₂CO₃ in ammoniacal mediumWhite ppt of SrCO₃Group V may be present
Confirmatory Tests
Flame test
Flame test moistened with conc. HCl		Crimson-red flameSr²⁺ is confirmed
Ammonium sulphate
Dissolve ppt in acetic acid and add (NH₄)₂SO₄		White ppt of SrSO₄Sr²⁺ is confirmed

Ionic equations

  • Sr²⁺ + CO₃²⁻ → SrCO₃ ↓
  • Sr²⁺ + SO₄²⁻ → SrSO₄ ↓

Result

The given salt contains Sr²⁺ as the cation (basic radical) and Cl⁻ as the anion (acidic radical). The salt is Strontium Chloride (SrCl₂).

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 crimson flame?

    Atomic emission of strontium.

  2. How is Sr distinguished from Ca?

    SrSO₄ ppts with (NH₄)₂SO₄; CaSO₄ is more soluble. Ca gives brick-red flame and oxalate ppt.

  3. How from Ba?

    Ba: apple-green flame and yellow BaCrO₄ in acetic acid.

  4. Why Group V?

    Carbonate ppt with (NH₄)₂CO₃ after earlier groups are absent.

  5. Why AgNO₃?

    Chloride anion.

  6. Why no Nessler?

    Not ammonium.

  7. Why HCl on the wire?

    Volatile chloride gives a better flame.

  8. Is SrCl₂ on the CBSE list?

    Sr²⁺ is a Group V cation in the qualitative analysis scheme.

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