Question

Which of the following compound does not gives ppt. with $dil.HCl$?

• A. $AgN{O}_3$
• B. $Pb{\left(N{O}_3\right)}_2$
• C. $H{g}_2{\left(N{O}_3\right)}_2$
• D. $Cu{\left(N{O}_3\right)}_2$

Answer 1

The correct option is D $Cu{\left(N{O}_3\right)}_2$

The copper nitrate will dissolve readily in water to give a solution containing $\left[Cu\right(H_{2}O{)}_6{]}^2+$ ions (and nitrate ions, of course) which are blue. The reaction that then occurs is:

$\left[Cu\right(H_{2}O{)}_6{]}^{2+}+4C{l}^{-}\to [CuC{l}_4{]}^{2-}+6H_{2}O$
The $[CuC{l}_4{]}^{2-}$ ion is yellow (its different shape produces the big colour change) and this, mixed with the blue of the $\left[Cu\right(H_{2}O{)}_6{]}^{2+}$ ion gives various shades of green etc.