When 0.2 mol CrCl3.6H2O is treated with excess of AgNO3, 0.4 mol of AgCl are obtained. The formula of the complex is
One mole of AgNO3 precipitates one mole of chloride ion. If 0.2 mole compound gives 0.4 mole AgCl, that means there must be two free chloride ions per molecule. So the formula is:
[CrCl(H2O)5]Cl2.H2O