To Prepare a Pure Sample of the Complex Potassium Trioxalatoferrate (III), Kg[Fe(C2O4)3l . 3H20 

Chemistry Lab ManualNCERT Solutions Class 12 Chemistry Sample Papers

Theory
The complex potassium trioxalatoferrate(III) can be prepared by dissolving freshly prepared ferric hydroxide in a solution of potassium oxalate and oxalic acid.
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Requirements
Three beakers (250 mL), china dish, funnel, funnel-stand, glass-rod, wash bottle, tripod stand and wire gauze. Ferric chloride, oxalic acid hydrated, potassium oxalate and potassium hydroxide.

Procedure

  1. Dissolve 3.5 g of anhydrous ferric chloride 50 mL of distilled water in a 250 mL beaker.
  2. In another beaker dissolve 4 g of potassium hydroxide in 50 mL of water.
  3. Add KOH solution to FeCl3 solution in small portions with constant stirring. Filter the precipitates of ferric hydroxide so formed through a buchner funnel. Wash the ppt. with distilled water.
  4. In another beaker (250 mL) take 4 g of hydrated oxalic acid and 5.5 g of hydrated potassium oxalate. Add about 100 mL of water and stir thoroughly to get a clear solution.
  5. Add the freshly prepared Fe(OH)3  ppt. in small amounts to the above solution with constant stirring. The ppt. get dissolved. If ppt. does not dissolve then warm it and leave the contents for sometime.
  6. Filter and transfer the filtrate to china dish and heat on a sand bath or wire-gauze to obtain crystallisation point.
  7. Now place the china dish on a beaker full of cold water and keep it aside for crystallisation. China dish should be covered with a black paper as the complex is sensitive to light.
  8. Decant off the mother liquor, wash the crystals with a small amount of ethyl alcohol and dry them between the folds of filter paper.
  9. Find out the weight of the crystals.

Observations
Weight of the crystals obtained = ………..g
Colour of the crystals is………..

Precautions

  1. Do not concentrate the solution too much.
  2. Let the concentrated solution cool slowly and undisturbed to get large crystals.