Question

When a metal rod $M$ is dipped into an aqueous colourless concentrated solution of compound $N$, the solution turns light blue. Addition of aqueous $NaCl$ to the blue solution gives a white precipitate $O$. Addition of aqueous $NH _{3}$ dissolves $O$ and gives an intense blue solution.
The final solution contains

• A. $\left[ Pb \left( NH _{3}\right)_{4}\right]^{2+}$ and $\left[ CoCl _{4}\right]^{2-}$
• B. $\left[ Al \left( NH _{3}\right)_{4}\right]^{3+}$ and $\left[ Cu \left( NH _{3}\right)_{4}\right]^{2+}$
• C. $\left[ Ag \left( NH _{3}\right)_{2}\right]^{+}$and $\left[ Cu \left( NH _{3}\right)_{4}\right]^{2+}$
• D. $\left[ Ag \left( NH _{3}\right)_{2}\right]^{+}$and $\left[ Ni \left( NH _{3}\right)_{e}\right]^{2+}$

Answer 1

Answer: (C)

$\underset{(N)}{ AgNO_{3}}+ NaCl \rightarrow \underset{( O )}{ AgCl \downarrow}+ NaNO _{3}$
$AgCl +2 NH _{3} \rightarrow\left[ Ag \left( NH _{3}\right)_{2}\right]^{+} Cl ^{-}$
$Cu \left( NO _{3}\right)_{2}+4 NH _{4} OH \rightarrow\left[ Cu \left( NH _{3}\right)_{4}\right]^{2+}$