An aqueous solution contains and . Out of these, how many ions will produce white precipitate with dilute HCl?

JEE MainChemistryModerateInorganic Chemistry

An aqueous solution contains
${Hg}^{2 +},{Hg}_{2}^{2 +},{Pb}^{2 +}{Ag}^{+},{Bi}^{3 +}$ and
${Cd}^{2 +}$ . Out of these, how many ions will produce white precipitate
with dilute HCl?

Show answer and solution

{Pb}^{2 +} + 2{Cl}^{-} \longrightarrow {PbCl}_{2} \downarrow (\ white\ );{Hg}_{2^{2 +}} + 2{Cl}^{-} \longrightarrow {Hg}_{2}{Cl}_{2} \downarrow (\ white\ )

{Ag}^{+} + {Cl}^{-} \longrightarrow AgCl \downarrow \ (white)\

K_{sp}

of chlorides of

{Pb}^{2 +}

and

{Hg}_{2}^{2 +}

is low as
compared to

K_{sp}

{Hg}^{2 +}

and

{Cd}^{2 +}

. Chloride ion
concentration provided by dilute HCl is just enough to exceed the

K_{sp}

{PbCl}_{2}

and

{Hg}_{2}{Cl}_{2}

. Thus

{Pb}^{2 +}

and

{Hg}_{2}^{2 +}

are precipitated as their chlorides.

Source: Grass-G / CH-28 Chemistry Paper FST 16 Jan.docx

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