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Experiment No. N

Analysis of Iron(III) Bromide (Fe(Br)₃)

Aim

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

Preliminary Test

  • Odor: Odorless
  • Texture: Crystalline
  • Color: White
  • Solubility: Soluble in water

Test of Anion

ExperimentObservationInference
Take 0.1 g of salt in a test tube and add conc. H₂SO₄ (or add MnO₂ if needed) and warmReddish brown fumes of bromine are evolvedBr⁻ may be present
Confirmatory Tests
Layer Test
Take 1 mL of neutralized extract, add CCl₄/CHCl₃ (or other suitable organic solvent), then add chlorine water dropwise and shake vigorously		Orange-brown colouration appears in the organic layerBr⁻ is confirmed
Silver Nitrate Test
Acidify sodium carbonate extract with dilute HNO₃ (or use water extract) and add AgNO₃		Pale yellow precipitateBr⁻ is confirmed

Test of Cation

ExperimentObservationInference
Original solution + NH₄OH solutionReddish-brown precipitateGroup-III cation may be present
Confirmatory Tests
Potassium Ferrocyanide Test
Dissolve the precipitate in dilute HCl, divide into two parts and add potassium ferrocyanide to one part		Blue/Prussian blue precipitateFe³⁺ is confirmed
Potassium Thiocyanate Test
To second part add potassium thiocyanate solution		Blood-red colouration is formedFe³⁺ is confirmed

Result

The given salt contains Fe³⁺ ions as cation and Br⁻ ions as anion. The salt is Fe(Br)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.