Question

Given the molecular formula of the hexa coordinated complexes (A) ${CoCl}_3.{6NH}_3$ (B) ${CoCl}_3.{5NH}_3$ (C) ${CoCl}_3.{4NH}_3$. If the number of coordinated ${NH}_3$ molecules in $A,B$ and $C$ respectively are $6,5$ and $4$, primary valency in $\left(A\right),\left(B\right)$ and $\left(C\right)$ are

• A. $0,1,2$
• B. $3,2,1$
• C. $6,5,4$
• D. $3,3,3$

Answer 1

Answer: (B)

$3,2,1$

The complex can be written as follows.

$A-\left[Co\right(N{H}_3{)}_6]C{l}_3$

$B-\left[Co\right(N{H}_3{)}_{5}Cl]C{l}_2$

$C-\left[Co\right(N{H}_3{)}_{4}C{l}_4]Cl$

Hence, number of primary valency are $3,2$ and $1$ respectively.