Question

The number of ions given by $\left[ {{\text{Pt}}{{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)}_{\text{6}}}} \right]{\text{C}}{{\text{l}}_{\text{4}}}$in aqueous solution will be:
A.two
B.three
C.five
D.eleven

Answer 1

Hint: $\left[ {{\text{Pt}}{{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)}_{\text{6}}}} \right]{\text{C}}{{\text{l}}_{\text{4}}}$ is a coordination compound. Coordination compounds do not furnish all the ions which are given by the constituent compounds and maintain their identity in aqueous solution. Only the ions attached to the complex will dissociate in a solution.

Complete step by step solution:
Coordination compounds are the compounds in which the central metal atom is linked to a number of ligands, which may be ions or neutral molecules, by coordination bond, i.e. by donation of lone pairs of electrons by these ligands to the central metal atom.
If this compound carries a positive or negative charge, it is called a complex ion. Hence, we can define coordination compounds as those compounds which contain complex ions. These complex ions are relatively stable and unlike double salts, they do not lose their identity in aqueous solution.
In the given question, ${\left[ {{\text{Pt}}{{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)}_{\text{6}}}} \right]^{{\text{4 + }}}}$is a complex cation. It remains as it is in aqueous solution.
In the given compound, $\left[ {{\text{Pt}}{{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)}_{\text{6}}}} \right]{\text{C}}{{\text{l}}_{\text{4}}}$, the cation ${\left[ {{\text{Pt}}{{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)}_{\text{6}}}} \right]^{{\text{4 + }}}}$is ionically bonded to four chloride ions. Thus, when dissolved in water, the compound dissociates as
$\left[ {{\text{Pt}}{{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)}_{\text{6}}}} \right]{\text{C}}{{\text{l}}_{\text{4}}} \rightleftharpoons {\left[ {{\text{Pt}}{{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)}_{\text{6}}}} \right]^{{\text{4 + }}}} + {\text{4C}}{{\text{l}}^ - }$
Hence, we can conclude that the number of ions given by $\left[ {{\text{Pt}}{{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)}_{\text{6}}}} \right]{\text{C}}{{\text{l}}_{\text{4}}}$ in aqueous solution is 5, namely one ${\left[ {{\text{Pt}}{{\left( {{\text{N}}{{\text{H}}_{\text{3}}}} \right)}_{\text{6}}}} \right]^{{\text{4 + }}}}$cation and four ${\text{C}}{{\text{l}}^{\text{ - }}}$anions.

Therefore, the correct answer is C.

Note: Coordination compounds are a type of additional compounds.
When a solution made by mixing two or more simple stable compounds in simple stoichiometric proportions is allowed to evaporate, crystals of new substances known as additional compounds separate out.
Apart from coordination compounds, the other type of addition compounds are double salts. Unlike coordination compounds, double salts are stable only in crystalline state and lose their identity in solution form.