Question

Match the color of precipitates listed in List 1 with the reagent(s) listed in List 2.

Answer 1

(a) $2B{i}^{3+}+3H_{2}S⟶B{i}_2{S}_3\downarrow Black+6H^{+}$
$B{i}^{3+}+3I^{-}⟶Bi{I}_2\downarrow Black$
(b) $C{u}^2++H_{2}S⟶CuS\downarrow Black+2H^{+}$
$C{u}^{2+}+2SC{N}^{-}⟶Cu(SCN{)}_2\downarrow Black$
Which on standing slowly changes to white
$2Cu(SCN{)}_2⟶2Cu(SCN)\downarrow white+(SCN{)}_2$
$C{u}_2{I}_2$ is white precipitate, and $C{u}_2\left[Fe\right(CN{)}_6]$ brown precipitate.
(c) $Z{n}^2++H_{2}S⟶ZnS\downarrow white+2H^{+}$
$2K^{+}+2\left[Fe\right(CN{)}_6{]}^{4-}+3Z{n}^{2+}⟶K_{2}Z{n}_3\left[Fe\right(CN{)}_6{]}_2\downarrow white$
$Zn{I}_2⟶soluble$
(d) $4A{g}^4+\left[Fe\right(CN{)}_6{]}^{4-}⟶A{g}_4\left[Fe\right(CN{)}_6]\downarrow white$
$A{g}^{+}+SC{N}^{-}⟶AgSCN\downarrow white$
$A{g}_{2}S\downarrow black$; $AgI\downarrow yellow$