Question

Presence of ${Fe}^{3+}$ in an aqueous solution can be made by addition of sodium acetate (in excess) when a reddish-brown colour is formed.

A blue colour solution is formed when potassium ferrocyanide in excess is added to aqueous ferric chloride solution. This blue colour is of__________.

• A. $\stackrel{II}{KFe}\left[\stackrel{III}{{Fe\left(CN\right)}_6}\right]$ or $\stackrel{III}{KFe}\left[\stackrel{II}{{Fe\left(CN\right)}_6}\right]$
• B. ${Fe}_4[{Fe\left(CN\right)}_6{]}_3$
• C. ${Fe}_3[{Fe\left(CN\right)}_6{]}_2$
• D. None of the above

Answer 1

The correct option is B ${Fe}_4[{Fe\left(CN\right)}_6{]}_3$

Fe(III) ions react with potassium ferrocyanide to give deep blue colour of ferric ferrocyanide.

$3K_4\left[Fe\right(CN{)}_6]+4FeC{l}_3\to {Fe}_4[{Fe\left(CN\right)}_6{]}_3+12KCl$.

Therefore, option B is correct.