Question

On treatment of $100\, mL$ of $0.1\, M$ solution of $CoCl _{3} \cdot 6 H _{2} O$ with excess $AgNO _{3} ; 1.2 \times 10^{22}$ ions are precipitated. The complex is

• A. $\left[ Co \left( H _{2} O \right)_{6}\right] Cl _{3}$
• B. $\left[ Co \left( H _{2} O \right)_{5} Cl \right] Cl _{2} \cdot H _{2} O$
• C. $\left[ Co \left( H _{2} O \right)_{4} Cl _{2}\right] Cl \cdot 2 H _{2} O$
• D. $\left[ Co \left( H _{2} O \right)_{3} Cl _{3}\right] \cdot 3 H _{2} O$

Answer 1

Answer: (B)

Millimoles of $AgNO _{3}=\frac{1.2 \times 10^{22}}{6 \times 10^{23}} \times 1000=20$

Millimoles of $CoCl _{3} \cdot 6 H _{2} O =0.1 \times 100=10$

$\therefore $ Each mole of $CoCl _{3} \cdot 6 H _{2} O$ gives two chloride ions.

$\therefore \left[ Co \left( H _{2} O \right)_{5} Cl \right] Cl _{2} \cdot H _{2} O$