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ChemLab113-0068 - thoroughly clean and rinse with distilled...

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Unformatted text preview: thoroughly clean and rinse with distilled water four of your test tubes, five of your smaller beakers and your volumetric flask, and leave them in your drawer to dry. This glassware will be needed at the beginning of the period when you carry out the next experiment. When you take the crystals from the oven, grind them well with the mortar and pestle and transfer them to the preweighed vial, weigh the vial again, and store it in your desicooler. Return the filter crucible and mortar and pestle. Finally, take your data to the computer you have been using and follow the directions on the screen. What the Computer Does The computer calculates a percentage yield of product. The data in the following table Will be used to show how that is done. Synthesis of Potassium Tris-Oxalatoferrate (ill) Trihydrate Mass of empty vial 22.43 g Mass of via] plus product 25.28 g Calculation of the theoretical yield is based on FeCl; being the limiting reagent. To show that FeC13 is limiting in this case we begin by calculating the numbers of moles of FeCl; and K2C204 used. You used 8.0 mL of a solution containing 0.24 g of FeCl; per mL of solution. Consequently, you used 8.0 times 0.24 g or 1.9 g of F6Ci3. The number of moles of FCCig used is calculated from that mass and the molar mass of FeC13 (162 gfmol). 19 lmol ‘g(162g Potassium oxalate was weighed out in the form of potassium oxalate monohydrate (K2C204-H20), a white, cwstalline solid that contains one water molecule for each K2C204 formula unit. Any given number of moles of K2C204-H20 contains that same number of moles of K2C204. Consequently, the number of moles of potassium oxalate used can be calculated from the mass of potassium oxalate monohydrate (12 g) and its molar mass (184 g/mol). ) = 0.012 mol ofFeCl3 1 mol 184 g 2 g( ) = 0.065 molofK2c,o, .H,0 = 0.065 molofK2C204 The chemical equation in the introduction shows that K2C204 and FeCl; react in a three-to-one mole ratio. If the ratio of moles of K2C204 used to moles of FeC13 used exceeds three in a given case, FeC13 is the limiting reagent in that case. That mole ratio is 0.065 divided by 0.012 or 5.4 in this case, and FeCl:, is seen to be the limiting reagent. To calculate the theoretical yield we also use the fact that each mole of FeC13 reacted yields at most one mole of K3[Fe(C204)3]-3H20. Thus 0.012 mol of FeCl3 theoretically yields 0.012 mol of K3[Fe(C204)3]-3H20. The molar mass of potassium tris—oxalatoferrate (In) trihydrate (491 g/rnol) is used to calculate the corresponding mass of the product. 95 ...
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