An Analytical Chemist Is Given 1

An analytical chemist is given 1.546g of a solid coordination complex that definitely contains a Cox(C2O4)y complex with Co is in the Co 2+ oxidation state and Li counter-ions, and possibly also water. His mission is to determine its correct empirical formula. From the information given in the problem, determine the empirical formula. 1a) He takes the Cox(C2O4)y solid and chips off a 0.5103 g solid sample. He manages to dissolve this sample into a solution of about 150 mL of 2M sulfuric acid. He then titrates a 0.101 M solution of K2Cr2O7 into this Cox(C2O4)y analyte solution. The analyte solution remains colorless until the endpoint at which it turns yellow. The volume of 0.101 M K2Cr2O7 titrated in this experiment is 11.0mL. What is the weight % of the oxalate in the original sample and what is the mmol of oxalate/100.0 g of the complex? The equation should first be balanced K2Cr2O7(aq) + H2C2O4 + H+(aq) –> Cr3+(aq) + CO2(g) + H20(l) + K+(aq) 1b) After thinking it over, the analytical chemist decides that a precipitation would be more accurate (and easier) than spectrophotometry. Hence, he dissolves a 0.5168g sample of Cox(C2O4)y in 100.0 ml of aqueous solution and makes sure the Co2+ is freed from the Cox(C2O4)y with the addition of acid. He then adds an excess of ammonium phosphate, (NH4)3PO4, resulting in the precipitation of a red solid powder. Once completely dried, the mass of the red solid powder of Co3(PO4)2 is measured to be 0.1356 g. Determine the amount of Co2+ in the original sample. So, based on the calculations above, what is the empirical formula for the complex?

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