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Experiment No. N

Analysis of Cobalt(II) Acetate (Co(CH₃COO)₂)

Aim

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

Preliminary Test

  • Odor: Vinegar-like
  • Texture: Crystalline
  • Color: White
  • Solubility: Soluble in water

Test of Anion

ExperimentObservationInference
Take 0.1 g salt + dilute H₂SO₄Colourless vapours with vinegar-like smell evolveCH₃COO⁻ may be present
Confirmatory Tests
Ester Test
Take 0.1 g salt in a test tube with ethanol and a little conc. H₂SO₄, then heat		Fruity odour of ethyl acetate is developedCH₃COO⁻ is confirmed
Ferric Chloride Test
Add neutral ferric chloride solution to the salt solution		Deep red colour appears; on heating it disappears and a brown-red precipitate formsCH₃COO⁻ is confirmed

Test of Cation

ExperimentObservationInference
Original solution + H₂S gas in presence of NH₄OHBlack precipitate is formedGroup IV cation may be present
Dissolve the black sulphide precipitate in aqua regia and heatResidue remains in solution after evaporationCo²⁺ may be present
Confirmatory Test
Potassium Hexanitritocobaltate(III) Test
Neutralise with NH₄OH, acidify with dilute acetic acid and add strong potassium nitrite solution		Yellow precipitate is formedPresence of Co²⁺ is confirmed

Result

The given salt contains Co²⁺ ions as cation and CH₃COO⁻ ions as anion. The salt is Co(CH₃COO)₂.

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.