A dark green complex has the empirical formula CrCl ₃ 6 H ₂ O . When 1 mole of this complex is treated with excess AgNO ₃ solution, it yields exactly 1 mole of AgCl precipitate. What is the structural formula of the complex, and how many water molecules are lost per formula unit when it is placed over a dehydrating agent like concentrated H ₂ SO ₄ ?

Step-by-step solution

Precipitation of 1 mole of AgCl per mole of the complex indicates that there is only one ionisable chloride ion present outside the coordination sphere. To satisfy the secondary valency (coordination number) of 6 for chromium, the remaining two chloride ions and four water molecules must be present inside the coordination sphere as ligands. Therefore, the structural formula of the complex is [ Cr ( H ₂ O )₄ Cl ₂ ] Cl 2 H ₂ O . The water molecules present outside the coordination sphere (lattice water) are easily lo