Acidic ferric chloride solution on treatment with excess of potassium ferrocyanide gives a Prussian blue…

Acidic ferric chloride solution on treatment with excess of potassium ferrocyanide gives a Prussian blue coloured colloidal species. It is:
  1. HFeFe(CN)6
  2. K5FeFe(CN)62
  3. Fe4Fe(CN)63
  4. KFeFe(CN)6

Solution

If we add ferric chloride over potassium ferrocyanide, it forms a white precipitate that will become blue. The reaction is

FeCl3+K4Fe(CN)6⟶KFeFe(CN)6+3KCl

Being small quantity of ferric chloride, not all potassium is displaced.

Asked in: JEE Main 2021 (27 Aug Shift 1)

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