There are three salts that contain complex ions of chromium and have the molecular formula CrCl3 6H2O. Treating 0.248g of the first salt with a strong dehydrating agent resulted in a mass loss of 0.036g. Treating 248mg of the second salt with the same dehydrating agent resulted in a mass loss of 18 mg. The third salt did not lose any mass when treated with the same dehydrating agent. Addition of excess aqueous silver nitrate to 100.0 mL portions of 0.10 M solutions of each salt resulted in the formation of different masses of silver chloride: one solution yielded 1430 mg AgCl; another, 2860 mg AgCl; the third, 4290 mg AgCl. Two of the salts are green and one is violet. What are the probable structural formulas for these salts?

Question

There are three salts that contain complex ions of chromium and have the molecular formula CrCl3  6H2O.  Treating 0.248g of the first salt with a strong dehydrating agent resulted in a mass loss of 0.036g.  Treating 248mg of the second salt with the same dehydrating agent resulted in a mass loss of 18 mg.  The third salt did not lose any mass when treated with the same dehydrating agent.  Addition of excess aqueous silver nitrate to 100.0 mL portions of 0.10 M solutions of each salt resulted in the formation of different masses of silver chloride: one solution yielded 1430 mg AgCl; another, 2860 mg AgCl; the third, 4290 mg AgCl.  Two of the salts are green and one is violet.  What are the probable structural formulas for these salts?

DrBob222 · Answer

A big hint: The loss in water from the dehydration experiments will tell you which H2O molecules were "more or less free" (; i.e., in or out of the coordination sphere of the central metal). The same with the ppt of AgCl will tell you which had Cl in the coordination sphere(were covalent and would not ppt AgCl) and which were outside the sphere (and would ppt AgCl). Post your work if you get stuck.

scac · Answer

scac