Question

What is the oxidation state of Fe in the product formed when acidified potassium ferrocyanide ( K​​​​​​4[Fe(CN6)] is treated with hydrogen peroxide ? How ?

Answer 1

Potassium hexacyanoferrate(III) react with potassium hydroxide and hydrogen peroxide 2K₃[Fe(CN)₆] + 2KOH + H₂O₂ → 2K₄[Fe(CN)₆] + O₂ + 2H₂O The K stands for potassium, which usually has a +1 charge. There are 4 of them, totaling +4 charge. Therefore the coordination complex must have a -4 charge for the total compound to have a zero charge. Since each cyanide ligand has a -1 charge, the central metal iron must have a +2 charge.

The oxidation number of Fe in K₄Fe(CN)₆ can be calculated as follows,

4(+1) + x + 6(-1) = 0

Hence x = +2
the oxidation state of Fe is +2