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A solution containing 2.675 g of CoCl3. 6 NH3 (molar mass = 267.5 g mol−1) is passed through a cation exchanger. The chloride ions obtained in solution were treated with excess of AgNO3 to give 4.78 g of AgCl (molar mass = 143.5 g mol−1). The formula of the complex is (At. mass of Ag = 108 u)

1. [Co(NH3)6]Cl3
2. [CoCl2(NH3)4]Cl
3. [CoCl3(NH3)3]
4. [CoCl(NH3)5]Cl2

Correct answer: [Co(NH3)6]Cl3

Solution

The correct option, [Co(NH3)6]Cl3, indicates that all six ammonia ligands are coordinated to the cobalt ion, which is consistent with the stoichiometry of the reaction and the amount of chloride ions released, as evidenced by the formation of AgCl from the chloride ions.

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