3 moles of metal complex with formula
Question:

3 moles of metal complex with formula $\mathrm{Co}(\mathrm{en})_{2} \mathrm{Cl}_{3}$ gives 3 moles of silver chloride on treatment with excess of silver nitrate. The secondary valency of Co in the complex is___________.

(Round off to the nearest integer)

Solution:

$3\left[\mathrm{Co}(\mathrm{en})_{2} \mathrm{Cl}_{2}\right] \mathrm{C} \ell+\underset{\text { (excess) }}{\mathrm{AgNO}_{3}} \rightarrow \underset{\text { (white ppt.) }}{3 \mathrm{AgCl}}$

Secondary valency of $\mathrm{Co}=6$

(C. N.)