Question

A solution containing a group-IV cation gives a precipitate on passing $H_{2}S$. A solution of this precipitate in $dil.HCl$ produces a white precipitate with basic $NaOH$ solution and bluish-white precipitate with basic potassium ferrocyanide. The cation is:

• A. $N{i}^{2+}$
• B. $C{o}^{2+}$
• C. $M{n}^{2+}$
• D. $Z{n}^{2+}$

Answer 1

The correct option is D $Z{n}^{2+}$

$Z{n}^{2+}$ ions react with $H_{2}S$ to form white precipitate of $ZnS$
$Z{n}^{2+}+H_{2}S\to ZnS\downarrow +2H^{+}$
$ZnS$ and $MnS$ are soluble in cold dil $HCl$ while $NiS$ and $CoS$ are insoluble.
$ZnS$ produces white precipitate of $zinchydroxide$ with $NaOH$
$ZnS+2NaOH\to Zn(OH{)}_2\downarrow +N{a}_{2}S$
$ZnS$ forms bluish white ppt with basic $potassiumferrocyanide$
$2ZnS+K_4\left[Fe\right(CN{)}_6]\to Z{n}_2[Fe\left(CN{)}_6\right]\downarrow \text{( bluish white)}+2K_{2}S$