Question

Only two-third of the chlorine contained in the solution of the complex salt $CoC{l}_3\cdot 5N{H}_3$ were precipitated from it by silver nitrate. No cobalt or free ammonia were detected in the solution of the salt.

The electrical conductivity of the solution shows that the salt dissociates into three ions. What is the coordination structure of the complex salt?

• A. $\left[Co\right(N{H}_3{)}_{5}Cl{]}^{2+}+2C{l}^{-}$
• B. $\left[Co\right(N{H}_3{)}_{5}Cl{]}^{2+}+2C{l}^{2-}$
• C. $\left[Co\right(N{H}_3{)}_{5}Cl{]}^{2-}+2C{l}^{-}$
• D. None of the above

Answer 1

The correct option is A $\left[Co\right(N{H}_3{)}_{5}Cl{]}^{2+}+2C{l}^{-}$

$CoC{l}_3\cdot 5N{H}_3$
Only two-third of the chlorine contained in the solution of the complex salt were precipitated from it by silver nitrate to form silver chloride. It means there are 2 chlorine atoms outside of coordination sphere. Since there is no ammonia detected it means ammonia is inside the coordination sphere. SO the formula for the complex is $[CoCl\cdot 5N{H}_3]C{l}_2$