Question

A co-ordination complex compound of cobalt has the molecular formulae 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 with excess of $AgNO_{3},$ $AgCl$ precipitate. The ionic formula for this complex would be:

• A. $\lbrack Co(NH_{3})_{5}(NO_{2})\rbrack Cl_{2}$
• B. $\lbrack Co(NH_{3})_{5}Cl\rbrack\lbrack Cl(NO_{2})\rbrack$
• C. $\lbrack Co(NH_{3})_{4}(No_{2})Cl\rbrack\lbrack(NH_{3})Cl\rbrack$
• D. $\lbrack Co(NH_{3})_{5}\rbrack\lbrack(NO_{2})_{2}Cl_{2}\rbrack$

Answer 1

Answer: (A)

$\lbrack Co(NH_{3})_{5}(NO_{2})\rbrack Cl_{2}$

Answer 2

The most probable complex which gives three moles ions in aqueous solution may be $\lbrack Co(NH_{3})_{5}NO_{2}\rbrack Cl_{2}$ because it gives two chlorine atoms on ionisation.

$\lbrack Co(NH_{3})_{5}NO_{2}\rbrack Cl_{2} \rightarrow \lbrack Co(NH_{3})_{5}NO_{2}\rbrack^{2 +} + 2Cl^{-}$