A solution containing 2.675 g of CoCl3.6NH3 (molar mass = 267.5 g/mol) 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). The formula of the complex is: (At. Mass of Ag = 108 u) [Co(NH3)6]Cl3, [CoCl2(NH3)4]Cl, [CoCl3(NH3)3], [CoCl(NH3)5]Cl2

Moles of CoCl3.6NH3 = 2.675 g / 267.5 g/mol = 0.01 mol
Moles of AgCl formed = 4.78 g / 143.5 g/mol = 0.0333 mol
Since AgCl is formed from Cl-, moles of Cl- = moles of AgCl = 0.0333 mol
Let the formula of the complex be [CoClx(NH3)6-x]Cl3-x
1 mole of complex gives (3-x) moles of Cl-
0.01 mol of complex gives 0.01(3-x) moles of Cl-
0.01(3-x) = 0.0333
3 - x = 3.33
x = -0.33 which is not possible. This indicates a calculation error or an incorrect assumption.
Let's reconsider the stoichiometry.
The moles of the complex is 0.01 mol.
The moles of chloride ions obtained are 0.0333 mol.
Therefore, the ratio of moles of chloride ions to moles of the complex is 0.0333 mol / 0.01 mol = 3.33 ≈ 3
This means that there are approximately 3 chloride ions per complex molecule. However, the number of chloride ions must be a whole number. The discrepancy is due to experimental error. The closest whole number to 3.33 is 3.
Considering the options, only [Co(NH3)6]Cl3 and [CoCl(NH3)5]Cl2 have three chloride ions per formula unit. If the complex is [Co(NH3)6]Cl3, all three chlorides will be released in the cation exchanger.
If the complex is [CoCl(NH3)5]Cl2, only two chlorides will be released, while the third chloride is coordinated to Cobalt.
Since we obtained 0.0333 moles of Cl-, which is close to 3 times the moles of the complex (0.01 mol), the formula of the complex is likely [Co(NH3)6]Cl3. The slight discrepancy is attributable to experimental error in measuring the mass of AgCl.