Place the thermometer in the solution carefully heat

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thermometer using a ringstand, clamp, and split one-hole stopper. Place the thermometer in the solution. Carefully heat the solution to 40ºC. Obtain 20 mL of 3% H 2 O 2 (hydrogen peroxide) in a 25 mL graduated cylinder. Add the 20 mL of H 2 O 2 very slowly (a few drops at a time) stirring continuously and keeping the temperature near 40ºC. A small amount of a slimy red precipitate [iron(III) hydroxide, Fe(OH) 3 ] might appear briefly. After adding all the hydrogen peroxide, heat to boiling. To the boiling solution add 8 mL of 1 M H 2 C 2 O 4 —the first 5 mL all at once and the last 3 mL very slowly—keeping the solution boiling. Set up a funnel with filter paper on a ringstand and gravity filter the boiling solution into a clean plastic specimen cup (see Figure 2.2 on the following page).
Experiment 2: Synthesis of Potassium Ferric Oxalate Trihydrate 2 – 4 Figure 2.2: Gravity filtration. Allow the solution to cool to room temperature, and then add 10 mL of ethanol to the plastic cup. Cover the plastic cup with its lid, and place it in your laboratory desk until the next laboratory period. The reason that the plastic cup should be placed in your desk is that the product, potassium ferric oxalate trihydrate [K 3 Fe(C 2 O 4 ) 3 · 3H 2 O], decomposes in the presence of light. The products of the decomposition are carbon dioxide [from the oxidation of C 2 O 4 2– ] and a complex of Fe 2+ (from the reduction of Fe 3+ ). The beaker is covered to prevent complete evaporation of the water. Complete evaporation of the water would make it impossible to separate the pure K 3 Fe(C 2 O 4 ) 3 · 3H 2 O crystals from the other salts, which would have remained in solution. Also, slower solvent evaporation encourages the development of larger, purer crystals. Week 2: Determine and record the mass of a piece of filter paper. Assemble a gravity filtration setup (see Figure 2.2 above) using a second filter paper. Using a stirring-rod equipped with a rubber policeman, transfer the crystals of K 3 Fe(C 2 O 4 ) 3 · 3H 2 O from the plastic cup to the filter paper in the funnel. When the crystals are free of solution, remove the filter paper and transfer the crystals (using your rubber policeman) to the previously massed, dry piece of filter paper resting atop a watchglass; spread the crystals out on the filter paper so they can air-dry.
Experiment 2: Synthesis of Potassium Ferric Oxalate Trihydrate 2 – 5 Obtain the combined mass of the filter paper and crystals. Determine the mass of K 3 Fe(C 2 O 4 ) 3 · 3H 2 O by subtraction. Show your crystals to your instructor. Waste Disposal: Place K 3 Fe(C 2 O 4 ) 3 · 3H 2 O crystals in the labeled collection bottle. All other chemical waste is to be flushed down the sink with plenty of water.

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