Question

$K_4\left[Fe\right(CN{)}_6]$ can be used to detect:

• A. $F{e}^{2+},F{e}^{3+}$
• B. $F{e}^{3+},Z{n}^{2+},C{u}^{2+}$
• C. $F{e}^{2+},F{e}^{3+},Z{n}^{2+},C{u}^{2+}$
• D. All of the above
  

Answer 1

The correct option is D All of the above

$K_4\left[Fe\right(CN{)}_6]$ can be used to detect all the below ions.
(A) $F{e}^{2+}$ reacts with potassium ferrocyanide to form white precipitate of $K_{2}Fe\left[Fe\right(CN{)}_6]$.
$F{e}^{2+}+2K^{+}\left[Fe\right(CN{)}_6{]}^{4-}\to K_{2}Fe\left[Fe\right(CN{)}_6]\downarrow (\text{white ppt.})$

(B) $F{e}^{3+}$ reacts with potassium ferocyanide to form potassium blue precipitate of ferric ferro cyanide.
$F{e}^{3+}+\left[Fe\right(CN{)}_6{]}^{-4}\to F{e}_4\left[Fe\right(CN{)}_6{]}_3\left(\text{prussian blue ppt.}\right)$

(C) $Z{n}^{2+}$ reacts with potassium ferocyanide to form white ppt of zinc ferrocyanide.
$Z{n}^{2+}+2K^{+}\left[Fe\right(CN{)}_6{]}^{4-}\to K_{2}Ca\left[Fe\right(CN{)}_6]\downarrow (\text{white ppt.})$

(D) $C{u}^{2+}$ reacts with potassium ferrocyanide to form choclate brown ppt of cupric ferrocyanide.
$C{u}^{+}+2K^{+}\left[Fe\right(CN{)}_6{]}^{4-}\to C{u}_2\left[Fe\right(CN{)}_6]\downarrow (\text{chocolate brown ppt.})$

(E) $C{a}^{2+}$ reacts with pottasium ferrocyanide to form white ppt of complex.
$C{a}^{2+}+K_4\left[Fe\right(CN{)}_6]\to K_{4}Ca[Fe\left(CN{)}_6\right]$