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Experiment No. N

Analysis of Arsenic(III) Oxalate ((As)₂(C₂O₄)₃)

Aim

To determine the presence of anion and cation in the given salt

Preliminary Test

  • Odor: Odorless
  • Texture: Crystalline
  • Color: White
  • Solubility: Slightly soluble in water

Test of Anion

ExperimentObservationInference
Take 0.1 g salt and add conc. H₂SO₄Colourless gases are evolved. On testing further, CO₂ and CO are evolvedC₂O₄²⁻ may be present
Confirmatory Tests
Calcium Chloride Test
Acidify extract with acetic acid and add calcium chloride		White precipitate of calcium oxalate is obtainedC₂O₄²⁻ is confirmed
KMnO₄ Test
Filter and add dilute H₂SO₄ to the precipitate, then dilute KMnO₄ and warm		KMnO₄ pink colour is dischargedC₂O₄²⁻ is confirmed

Test of Cation

ExperimentObservationInference
Original solution + H₂S gas in presence of dil. HCl and NH₄ClYellow precipitate is formedGroup-II-B (As³⁺) may be present
Confirmatory Test
Ammonium Molybdate Test
Treat the dissolved precipitate with concentrated nitric acid and ammonium molybdate solution		Canary yellow precipitate is formedPresence of As³⁺ is confirmed

Result

The given salt contains As³⁺ ions as cation and C₂O₄²⁻ ions as anion. The salt is (As)₂(C₂O₄)₃.

Precautions

  1. Handle the chemicals with care.
  2. Don't use excess of chemicals.
  3. Keep the mouth of the test tube away from the face.