The overall goal of this lab was to produce an unknown oxalate compound, find its percent composition, calculate its molecular formula, and determine the limiting reactant in its formation. A reaction between iron III chloride hexahydrate and potassium oxalate monohydrate produced 3.307g of potassium trioxalatoferrate (III) trihydrate with a 62.0 percent yield. A permanganate titration determined the average percent composition of oxalate was 53.3% with a 2.22% standard deviation. The percent composition revealed the compound’s empirical formula to be FeK3(C2O4)3•3H2O. Potassium oxalate proved to be the limiting reactant.
Results and Discussion
The potassium trioxalatoferrate (III) trihydrate was produced by reacting 6 grams of potassium oxalate
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Carbon dioxide and water in the solution were also clear. Once the solution was completely titrated, Mn7+ ions remained unreduced and changed the color of the solution to pink. The KMnO4 was added to each solution until the oxalate solution reached the end point and changed to an extremely light pink color. The change in volume in the burette of the potassium permanganate recorded in all three trials was used to calculate the moles of oxalate in the 0.100-gram compound, giving the percent composition of the compound. The three trials reacted 27.95 mL, 26.61 mL, and 25.74 mL of potassium permanganate to determine 55.7%, 53.0%, and 51.3% respectively of oxalate in the compound with a 53.3% average. To calculate the empirical formula of the compound, the percent composition of the each piece of the compound needed to be found. A thermogravimetric analysis performed outside the lab determined 11.0% of the compound was water and an inductively coupled plasma atomic emission spectroscopy found 11.3% was iron. Potassium accounted for the remaining 24.4% of the compound. The compound’s empirical formula was determined to be FeK3(C2O4)3•3H2O. With the molecular formula and the balanced equation for the synthesis of potassium trioxalatoferrate (III) trihydrate, stoichiometry revealed potassium oxalate monohydrate was the limiting reactant. The theoretical yield of 6 grams of potassium oxalate monohydrate was