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Experiment No. N

Analysis of Iron(II) Sulphide (FeS)

Aim

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

Preliminary Test

  • Odor: Odor of rotten eggs
  • Texture: Crystalline
  • Color: White
  • Solubility: Soluble in water

Test of Anion

ExperimentObservationInference
Warm the salt with dilute H₂SO₄Colourless gas with smell of rotten eggs is evolvedS²⁻ may be present
Confirmatory Tests
Lead Acetate Test
Pass gas through filter paper dipped in lead acetate solution		Paper turns blackS²⁻ is confirmed
Sodium Nitroprusside Test
Make solution alkaline with NH₄OH (or sodium carbonate extract) and add sodium nitroprusside solution		Purple/violet colouration is producedS²⁻ is confirmed

Test of Cation

ExperimentObservationInference
Salt solution + NaOH solutionDirty green precipitateFe²⁺ may be present
Confirmatory Test
Potassium Ferricyanide Test
Add potassium ferricyanide solution		Dark blue precipitate (Turnbull's blue)Presence of Fe²⁺ is confirmed

Result

The given salt contains Fe²⁺ ions as cation and S²⁻ ions as anion. The salt is FeS.

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.