HS2 Chemistry unit 5 Coordination Compounds experiments

 

Experiment: Preparation of a Coordination Compound

Aim:
To prepare a sample of the coordination compound potassium tris(oxalato)ferrate(III), K₃[Fe(C₂O₄)₃]·3H₂O.

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Materials Required:

• Ferrous sulfate (FeSO₄·7H₂O)

• Oxalic acid (H₂C₂O₄·2H₂O)

• Potassium oxalate monohydrate (K₂C₂O₄·H₂O)

• Hydrogen peroxide (H₂O₂, 6%)

• Acetone

• Distilled water

• Beakers, glass rods, funnel, filter paper, measuring cylinders, and other standard lab apparatus

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Procedure:

1. Preparation of Iron(III) Oxalate Complex:

   • Dissolve about 5 g of ferrous sulfate in 25 mL of warm distilled water.

   • Add 3 g of oxalic acid to the solution, stir and heat gently. A greenish-yellow precipitate of ferrous oxalate will form.

   • Filter the precipitate and wash it with small amounts of cold water.

2. Formation of Potassium Tris(oxalato)ferrate(III):

   • Transfer the wet ferrous oxalate precipitate into a beaker containing 20 mL of 6% hydrogen peroxide.

   • Stir the mixture gently. The ferrous ion will oxidize to ferric ion, forming a yellow solution of ferric oxalate.

   • Add 2 g of potassium oxalate to the solution while stirring.

   • Heat the mixture slightly (not boiling) to complete the reaction.

3. Crystallization:

   • Cool the solution and add an equal volume of acetone to induce crystallization.

   • Allow the solution to stand undisturbed for 15–20 minutes.

4. Filtration and Drying:

   • Filter the crystals formed using filter paper and a funnel.

   • Wash the crystals with a small amount of acetone.

   • Dry the crystals between filter papers or in a desiccator.

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Observation:

Yellow-green crystals of potassium tris(oxalato)ferrate(III) are obtained.

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Precautions:

• Handle hydrogen peroxide with care; it's a strong oxidizing agent.

• Avoid prolonged heating to prevent decomposition of the complex.

• Use distilled water throughout to avoid contamination.