Question

If excess of $AgN{O}_3$ solution is added to 100 mL of a 0.024 M solution of dichlorobis (enthylenediamine) cobalt (III) chloride, how many moles of AgCl be precipitated?

• A. 0.0012
• B. 0.0016
• C. 0.0024
• D. 0.0048

Answer 1

The correct option is C 0.0024

The co-ordination sphere of complex contains $C{o}^{3+}+2C{l}^{-}+2\left(en\right)$. Net charge on co-ordination sphere $=+3+2(-1)+2\left(0\right)=+1$.
Thus, complex is $\left[Co\right(en{)}_{2}C{l}_2{]}^{+}C{l}^{-}$. It can dissociate as
$\left[Co\right(en{)}_{2}C{l}_2{]}^{+}C{l}^{-}\to \left[Co\right(en{)}_{2}C{l}_2{]}^{+}+C{l}^{-}$
Only one $C{l}^{-}$ (per complex molecule) comes into solution which is precipitated as AgCl.

100 mL of 0.024 M complex $=0.024mol/L\times \frac{100mL}{1000mL/L}=0.0024$ mol.

The number of moles of AgCl formed $=$ the number of moles of complex $=0.0024$ mol.