question_answer

One mole of \[CoC{{l}_{3}}.YN{{H}_{3}}\]complex compound on complete ionisation in water produces three moles of ions. If one chloride satisfies both primary and secondary valencies of cobalt ion, the value of Y is

A)  3                                            

B)  4

C)  5                                            

D)  6

Correct Answer: C

Solution :

                 Since, the coordination number of Co is 6, there must be six ligands inside the coordination sphere. As one mole of complex give three moles of ions, two \[\text{C}{{\text{l}}^{-}}\]ions must present outside the sphere. Hence, the formula of the complex is \[[Co{{(N{{H}_{3}})}_{5}}Cl]C{{l}_{2}}.[Co{{(N{{H}_{3}})}_{5}}Cl]C{{l}_{2}}\]\[\xrightarrow{\text{Ionisation}}\underbrace{{{[Co{{(N{{H}_{3}})}_{5}}Cl]}^{2+}}+2\text{C}{{\text{l}}^{-}}}_{\text{3 }\,\text{ions}}\] In this complex one Cl atom satisfies both primary and secondary valencies as Hence, the value of Y is 5.