# FeCl3 on reaction with potassium ferrocyanide in aqueous solution gives blue colour.When 0.01M of FeCl3 and 0.1M potassium ferrocyanide are placed in a beaker and seperated by a semi permeable membrane, identify whether there will be an appearance of blue colour on potassium ferrocyanide side due to osmosis.E xplain your answer.

The equation for the reaction of FeCl3 and K4 [Fe(CN)6] is

4 FeCl3 + 3 K4 [Fe(CN)6]
Fe4[Fe(CN)6] + 12 KCl
Ferri-ferro cyanide
Therefore the blue colour of the solution is due to the formation of ferri-ferro cyanide complex. When 0.01M of FeCl
3and 0.1M potassium ferrocyanide are placed in a beaker and seperated by a semi permeable membrane the movement of only water molecules will take place across the membrane from FeCl3 side to potassium ferrocyanide side due to osmosis (Osmosis is the diffusion of solvent molecules through a semi permeable membrane into a region of high solute concentration) . The movement of water molecules will stop when there equal concentration of solutions on both sides of the membrane. This means that no FeCl3molecules would move across the membrane to potassium ferrocyanide side. Hence there will be no formation of ferri-ferro cyanide complex because of which blue colour will not appear in potassium ferrocyanide side.

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