Question

A complex compound of cobalt has molecular formula containing five ${{N}}{{{H}}_3}$ molecules, one ${{N}}{{{O}}_2}$ group and two ${{Cl}}$ atoms for one cobalt atom. One mole of this compound produces three moles of ions in aqueous solution. On reacting with an excess of ${{AgN}}{{{O}}_3}$ solution, two moles of ${{AgCl}}$ get precipitated. The ionic formula of the compound is:
A. $\left[ {{{Co}}{{\left( {{{N}}{{{H}}_3}} \right)}_4}{{N}}{{{O}}_2}{{Cl}}} \right]\left[ {\left( {{{N}}{{{H}}_3}} \right){{Cl}}} \right]$
B. $\left[ {{{Co}}{{\left( {{{N}}{{{H}}_3}} \right)}_5}{{Cl}}} \right]\left[ {{{Cl}}\left( {{{N}}{{{O}}_2}} \right)} \right]$
C. $\left[ {{{Co}}{{\left( {{{N}}{{{H}}_3}} \right)}_5}\left( {{{N}}{{{O}}_2}} \right)} \right]\left[ {{{C}}{{{l}}_2}} \right]$
D. $\left[ {{{Co}}{{\left( {{{N}}{{{H}}_3}} \right)}_5}} \right]\left[ {\left( {{{N}}{{{O}}_2}} \right){{C}}{{{l}}_3}} \right]$

Answer 1

Hint:Silver nitrate can be referred to as an inorganic compound. It has a trigonal planar shape. In this compound, silver is coordinately bonded with three nitrate ions. It has an ability to extract halide ions in many inorganic reactions.

Complete answer:
The coordination isomers have a cationic part which has positive charge and an anionic part which has a negative charge. They interchange one or more ligands. Actually, they can be termed as coordination salts. But they are exchanged between two metal atoms. Here, there is only one atom. So it is not sure that the given compounds in options can be referred to as coordination isomers.
It is given that the complex compound has molecular formula containing five ${{N}}{{{H}}_3}$ molecules, one ${{N}}{{{O}}_2}$ group and two ${{Cl}}$ atoms for one cobalt atom.
When the complex is reacted with ${{AgN}}{{{O}}_3}$ solution, two moles of ${{AgCl}}$ are precipitated. This defines that the two chloride ions formed will be outside the coordination sphere. Only then, It is able to react with ${{AgN}}{{{O}}_3}$ and produces two moles of ${{AgCl}}$. The chloride ion inside the coordination sphere is difficult to make it react with ${{AgN}}{{{O}}_3}$.
The reaction between the complex and ${{AgN}}{{{O}}_3}$ is given below:
$\left[ {{{Co}}{{\left( {{{N}}{{{H}}_3}} \right)}_5}\left( {{{N}}{{{O}}_2}} \right)} \right]\left[ {{{C}}{{{l}}_2}} \right] + {{AgN}}{{{O}}_3} \to {\left[ {{{Co}}{{\left( {{{N}}{{{H}}_3}} \right)}_5}\left( {{{N}}{{{O}}_2}} \right)} \right]^{2 + }} + 2{{C}}{{{l}}^ - }$
This is possible only in the option C. Two chloride ions are present only in the option C. There are more or less chloride ions present in other options.

Hence, the correct option is C.

Note:
Thus we can confirm that the complex compound gives a total of two moles of chloride ions and one mole of pentaammine nitrito-N-cobalt(III) ions. Thus it gives a total three moles of ions in solution as they are the primary valencies.