Question

A colourless aqueous solution contain nitrates of two metal, when it is added to an aqueous solution of $NaCl$, a white precipitate ws formed. This precipitate was found to be partially soluble in hot water to give a residue $P$ and a solution $Q$. The residue $P$ was solublein aq. in $N{H}_3$ and also in excess sodium thiosulfate. The hot solution $Q$ gave a yellow precipitate with $KI$. The metals $X$ and $Y$, respectively, are:

• A. $Ag\text{and}Cd$
• B. $Ag\text{and}Pb$
• C. $Cd\text{and}Pb$
• D. $Cd\text{and}Zn$

Answer 1

The correct option is B $Ag\text{and}Pb$

$x=Ag;y=Pb;P=AgCl:Q=PbC{l}_2$
(1) $$\begin{array}{ccccc}AgN{O}_3& +NaCl& \to & AgCl\downarrow +& NaN{O}_3\\ x& & & P& \end{array}$$

(2) $$\begin{array}{cccc}AgCl\left(s\right)& +& 2N{H}_3& \to {\left[Ag{\left(N{H}_3\right)}_2\right]}^{+}C{l}^{-}\\ \left(P\right)& & & \text{(soluble complex)}\end{array}$$

(3) $$\begin{array}{ccccc}AgCl+& 2N{a}_2{S}_2{O}_3& \to & N{a}_3\left[Ag\right(S_2{O}_3\left)\right]& +NaCl\\ \text{Residue P}& \left(Excess\right)& & \left(\text{Soluble complex}\right)& \end{array}$$
(4)
$$\begin{array}{cc}Pb{\left(N{O}_3\right)}_2& +2NaCl\to PbC{l}_2\downarrow +2NaN{O}_3\\ \left(y\right)& \text{white ppt (Q)}\end{array}$$

(5) $$\begin{array}{ccccc}PbC{l}_2& +& 2KI\to & Pb{I}_2+& 2KCl\\ \text{(hot solution)}& & & \text{yellow ppt}& \\ Q& & & & \end{array}$$