Question

The sample is dissolved in hot con. $HCl$ and add few drops of $N{H}_{4}OH$, then acidified with dil. Acetic acid + few drops of potassium ferrocyanide solution. The precipitate obtained is chocolate brown in colour. Guess the presence of element present :

• A. ${Pb}^{2+}$
• B. ${Cu}^{2+}$
• C. ${Zn}^{2+}$
• D. ${Fe}^{2+}$

Answer 1

The correct option is B ${Cu}^{2+}$

Potassium ferrocyanide precipitates brown coloured copper(II) ferrocyanide from Cu²⁺ solutions. The equation can be written as:

$C{u}^{2+}+\left[Fe\right(CN{)}_6{]}^{4-}\to C{u}_2\left[Fe\right(CN{)}_6\left]\right(s\left)\right)$