Question

To a solution containing $C{a}^{2+},A{g}^{+}C{u}^{2+}$ and $K^{+},2MHCl$ is added when a white precipitate $\left(A\right)$ is obtained. After filtration $H_{2}S$ is passed through the filtrate, a black ppt. $\left(B\right)$ is formed. On removing $\left(B\right)$ by filtration, it gave a white ppt. $\left(C\right)$ with $N{a}_{2}C{O}_3$ solution. Identify $\left(A\right),\left(B\right)$ and $\left(C\right)$:

• A. $\left(A\right)-AgCl$
  $\left(B\right)-C{u}_{2}S(Blackppt.)$
  $\left(C\right)-CaC{O}_3$
• B. $\left(A\right)-AgCl$
  $\left(B\right)-CuC{O}_3(Blackppt.)$
  $\left(C\right)-CaC{O}_3$
• C. $\left(A\right)-AgCl$
  $\left(B\right)-CuS(Blackppt.)$
  $\left(C\right)-CaC{O}_3$
• D. $\left(A\right)-AgC{l}_2$
  $\left(B\right)-CuS(Blackppt.)$
  $\left(C\right)-CaO$

Answer 1

The correct option is C $\left(A\right)-AgCl$

$\left(B\right)-CuS(Blackppt.)$
$\left(C\right)-CaC{O}_3$
Option (C) is correct.
When salt containing $A{g}^{+}$ reacts with $HCl$, white ppt of $AgCl$ is formed.The filtrate obtained is warmed up and $H_{2}S$ gas is passed forming Black ppt. which confirms the presence of $c{u}^{2+}$ ions.The ppt. is filtered out and $N{a}_{2}C{O}_3$ is added in it which confirms the presence of $C{a}^{2+}$ ions thus,
$\left(A\right)AgCl\left(whiteppt\right)$
$\left(B\right)C{u}_{2}S(Blackppt.)$
$\left(C\right)CaC{O}_3\left(whiteppt\right)$