Question

What is the charge on $[Ag(CN{)}_2{]}^{-}$ ?
A) $+1$
B) $-1$
C) $+2$
D) $+3$

Answer 1

Hint:We know that $[Ag(CN{)}_2{]}^{-}$ is a coordinate compound, in which cyanide acts as a monodentate ligand. The chemical name of $[Ag(CN{)}_2{]}^{-}$ is Dicyanoargentate. The charge on $CN$ is $-1$ . In presence of potassium ions, this complex form Potassium dicyanoargentate $\left(1\right)$


Complete step by step solution:
We know that silver cyanide is a chemical compound with a molecular formula $AgCN$ . Silver ion is represented by $Ag$ and cyanide ion is represented by $CN$ . This silver cyanide is precipitated in presence of sodium cyanide to a solution containing silver ions. This precipitate further dissolves when we add cyanide ions and form $[Ag(CN{)}_2{]}^{-}$ . This complex has a linear structure and its name is Dicyanoargentate.
Now let's calculate the charge on this complex. Let the charge of $Ag$ being x. We know that the charge of $CN$ is $-1$ . Substituting the values according to the molecular formula $[Ag(CN{)}_2{]}^{-}$ we get
$\begin{array}{rl}& \Rightarrow x+2\times -1=-1\\ & \Rightarrow x=1\end{array}$
Thus the charge on the complex is $+1$ . Dicyanoargentate forms a coordinate compound. A coordinate compound is a compound in which a central atom, in this case, silver is surrounded by non-metal atoms, cyanide ions. Cyanide ions act as monodentate ligands. Cyanide ion is a monodentate ligand because it has only one co-ordination atom. In presence of potassium ions, this complex form Potassium dicyanoargentate $\left(1\right)$


Note:We should know what are coordinate bonds. It is also known as a dative bond. It is formed when the bonding electrons are shared by only one of the two atoms. It is a type of covalent bond. In $[Ag(CN{)}_2{]}^{-}$ , cyanide ions supply electrons and form coordinate bonds with silver.