Question

A coordination complex compound of cobalt has molecular formula containing five ammonia molecules, one nitro group and two chlorine atoms for one cobalt atom. One mole of this compound produces three mole ions in an aqueous solution.On reacting this solution with excess of silver nitrate solutions, two moles of AgCl get precipitated. The ionic formula of this complex would be

• A. $[Co(NH_3)_4NO_2Cl] [(NH_3)Cl]$
• B. $[Co(NH_3)_5Cl] [Cl(NO_2)]$
• C. $[Co(NH_3)_5(NO_2)]Cl_2$
• D. $[Co(NH_3)]_5.[(NO_2)_2Cl_2]$

Answer 1

Answer: (C)

$[Co(NH_3)_5(NO_2)]Cl_2$

Answer 2

The molecular formula of complex is $Co(NH_3)_5NO_2Cl_2$. As the one mole of compound produces two moles of AgCl with $AgNO_3(aq)$, it has two ionisable $Cl^-$ ions per molecule. Thus, possible ionic formula is $[Co(NH_3)_5NO_2]Cl_2$ It ionises to produce one $[Co(NH_3)_5NO_2]^{2+}$ and two $Cl^-$ ions i.e., in all three ions per molecule