Question

A coordination complex compound of cobalt has a molecular formula containing five ammonia molecules, one nitro group and two chlorine atoms for one cobalt atom. One mole of this compound produces three moles of ions in an aqueous solution. On reacting this solution, with excess of $AgN{O_3}$ solution two moles of $AgCl$ get precipitated. The ionic formula for this complex would be:
A. $[Co{(N{H_3})_4}{(NO)_2}Cl](N{H_3})Cl]$
B. $[Co{(N{H_3})_5}Cl]Cl(N{O_2})]$
C. $[Co(N{H_3})(N{O_2})]C{l_2}]$
D. $[Co{(N{H_3})_5}][{(N{O_2})_2}C{l_2}]$

Answer 1

Hint:Coordination complex retains their identity in the solution. These compounds do not give all their constituent ions when dissolved in water. In these compounds individual properties of some constituent ions are lost.

Complete answer:
Addition compounds are of two types. First is the coordination complex. Example $CuS{O_4}.4N{H_3}$. It does not give all its constituent solution. It gives only $S{O_4}^{2 - }$ and $C{u^{2 + }}$ ion is obtained as ${[Cu{(N{H_3})_4}]^{2 + }}$ ion which is called complex ion. Thus $CuS{O_4}.4N{H_3}$ is formulated as $[Cu{(N{H_3})_4}]S{O_4}$. Hence the solution will give a test for sulphate ion, and will not give the test for copper ion. This is a coordination compound.
Coordination complexes contain complex ions either positively or negatively. And there are some neutral complexes also which do not have any charge on it.
Coordination complexes have a metal center. The neutral molecules or ions which are attached to central metal ions in the complex are called ligands. Ligand donates one or more electrons to the metal ion. The central metal and ligand are written in [ ] box, and are called coordination spheres. The portion outside is called an ionization sphere. Thus copper and ammonia are present in the coordination sphere, and sulphate ion is in the ionization sphere.
The species written in the ionization sphere are ionisable, and hence precipitated in addition to precipitating agent. While those present in the coordination sphere are non- ionisable.
In the given question, one mole of compound gives 3 moles of ions, that means one will be a complex ion and the other two will be from an ionization sphere. Now in addition to $AgN{O_3}$ ( precipitating agent for chlorine ion) two mole of $AgCl$ we get. That clearly means that there were 2 chlorine ions present in the ionization sphere. And other ions were present in the coordination sphere.
$[Co{(N{H_3})_5}(N{O_2})]C{l_2} \to {[Co(N{H_3})(N{O_2})]^{2 + }} + 2C{l^ - }$

Therefore the correct option will be C.

Note:
The second addition compounds are double salt, which loses its identity in solution in water or in any ionic solution when dissolved in it. In these compounds individual properties of the constituent ions are not lost. For example $KCl.MgC{l_2}.6{H_2}O$