Synthesizing Sodium Ferrate - Lab Report Example

? 5 December SKILL-BUILDING EXERCISES This week’s module begins with four activities. First, sodium ferrate will be synthesized using a wet chemical method. Then the yield of sodium ferrate produced will be calculated. Next, Beer’s Law (see Appendix 1) will be used to convert absorbance readings to actual concentration values of ferrate. Last, a redox reaction involving sodium ferrate and a pharmaceutical pollutant will be performed and the rate of that reaction using information in the Excel spreadsheet will be measured. Part 1. Synthesizing Sodium Ferrate Solutions of FeCl3 are provided. Sodium ferrate forms with the following reaction: 2 FeCl3 + 3 NaClO + 10 NaOH > 2 Na2FeO4 + 9 NaCl + 5 H2O NaClO is an active component of bleach. Very concentrated solutions of bleach are used as “liquid chlorine” for swimming pools. NOTE: This synthesis will be performed in the fume hood. The solution will be very basic, so goggles will always be worn while performing this synthesis. Any solution got on hands will be immediately washed with soap and water. 20 mL of commercial bleach is to be poured into a 50 mL beaker. A stirring bar will be added to the beaker and placed on a stir plate. 10 g of NaOH pellets will be added to the beaker of bleach and stirring will be begun. This is an exothermic reaction so the beaker will get warm. 0.50 mL of 0.30 M FeCl3 will be pipetted using the plastic pipette into the dissolved NaOH solution while it is still warm. The mixture will be allowed to stir for approximately 10 minutes. The solution will be allowed to cool for another 3-5 minutes. The formation of the Na2FeO4 will cause the solution to appear purple. Any foam that appears on the surface will have to be removed by blotting with a paper towel. A suction filtration apparatus will be assembled with due consultation of the GSA). A sintered glass filter will be used on top of the vacuum filtration flask, the vacuum will be turned on and the sodium ferrate solution will be added slowly. This will filter the sodium ferrate solution. The liquid which passes through the filter (called the filtrate) is a concentrated solution of sodium ferrate. NOTE: A clean sintered glass filter makes the filtration faster. The volume of ferrate solution that was prepared using a graduated cylinder will be measured. The sodium ferrate solution will be stored in a plastic bottle. The bottle will be labeled with this information; Name of the Team Manager, “Sodium ferrate in water”, concentration of sodium ferrate (will be determined later), date, and the lab section number. Part 2. Calculation of the Percent Yield of Ferrate Produced In the reaction that was just performed, FeCl3 was the limiting reagent. After the theoretical yield (review is on pages133-139 in the textbook, Tro 2nd edition) of sodium ferrate has been calculated in moles, its theoretical concentration, in molarity (M) will be determined with the help of the total volume of solution that was measured in the Part 1. The actual concentration of sodium ferrate in the solution will be calculated with the help of the spectrophotometer and Beer’s Law. The SpectraVis spectrometer will be calibrated with the help of a cuvette of DI water. The SpectraVis should be in full spectrum mode when calibrating. The DI water will be removed with a plastic pipette so that all the water droplets from the inside corners as well as from the sides of the cuvette can be removed. The sodium ferrate solution will be added to the cuvette (slightly more than half full). The absorbance of the sodium ferrate solution will be recorded at 510 nm. NOTE: If the absorbance at 510 nm gets above 1.5, the ferrate solution in the cuvette will be diluted (not the original solution) until the absorbance is between 1.0 and 1.5. The volume of ferrate solution that was diluted as well as the amount of water which was added to calculate the concentration of the original ferrate solution will be kept track of. The ferrate solution will be removed from the cuvette with a disposable pipette and poured into a 10 mL graduated cylinder. The volume of the solution will be noted. A small amount of water mix will be added. This volume of solution will be noted and poured into the cuvette. The absorbance will be recorded at 510 nm of this diluted ferrate solution on the data sheet. The last three steps will be repeated again if the ferrate solution’s absorbance is still found to be above 1.5. The ferrate solution will be poured in a clean beaker (so that it can be used in DTZA oxidation experiment) and the cuvette will be rinsed out with DI water and will be discarded. It will be allowed to dry out. All steps beginning from the addition of the sodium ferrate solution to the cuvette will be repeated to record another absorbance value. The concentrations of ferrate in the original solution will be calculated with the Beer’s Law (Appendix 1) with the assumption that the path-length of the cuvette is 1.0 cm and the molar absorptivity, e, is 1150 M-1 cm-1. The dilution of the ferrate solution will be taken into account if the solution was originally diluted. The concentration values for both Trials will be recorded on the data sheet and the average concentration will be found. This will be the actual yield. The percent yield will be calculated based on the theoretical yield for the reaction. Also, the concentration on the container of sodium ferrate will be recorded for easy future reference. Part 3. Performing the Reaction between Ferrate and Diatrizoic Acid (DTZA) The reaction of ferrate and DTZA will be performed to determine how fast the reaction proceeds. The rate calculations for this reaction will be embedded in the Excel spreadsheet with the data that will be collected in the lab. The ferrate-DTZA reaction will be conducted twice. Results of the two FeO42--DTZA reactions should be very similar but they won’t be exactly the same due to experimental error (including human error and uncertainties that are inherent in the experimental process). This paragraph suggests the way to prepare for the reaction. The SpectraVis will be calibrated with DI water in full spectrum mode. The DI water will be discarded in a waste beaker. About 3 mL of the sodium ferrate solution will be poured in a cuvette and its absorbance will be measured at 510 nm. If the absorbance is above 1.5, it will be diluted with DI water as was done in the Part 2. This solution will be saved for the two reactions in this part of the skill-building exercise. It will be ensured that the cuvette is clean and dry before proceeding. 2.0 mL of 0.040 M DTZA stock solution will be acquired from the GSA. This paragraph explains how to perform the FeO42--DTZA reaction that will be completed twice. 1.5 mL of the 0.040 M DTZA solution will be pipetted into the cuvette. NOTE: The pipettes will be labeled, one for DTZA and the other for sodium ferrate. The pipettes will not be mixed up. The following steps will be performed together quickly and in this order; 1.5 mL of the FeO42- solution that was saved before will be added to the DTZA solution in the cuvette. A stop watch will be begun to record the time for each absorbance measurement as soon as the solutions get combined in the cuvette. The capped cuvette will be shaken vigorously for 5 seconds. The cuvette will be placed in the spectrometer and the absorbance will be measured. The time of this measurement will be noted. The time and absorbance value will be recorded on the data sheet. The cuvette will be taken out of the spectrometer and will be shaken vigorously to keep the solution mixed. The measured absorbance values will be recorded on the data sheet approximately every 30 seconds for 10 minutes. The exact times for which the absorbance is measured will be recorded. The ferrate-DTZA solution will be discarded in the waste beaker. The cuvette will be rinsed out well. Every step beginning from the cleaning and drying of the cuvette before proceeding till the rinsing out of the cuvette will be repeated. The work area will be cleaned up and the completed data sheets will be turned in. It will be ensured that the ferrate solution is given to the GSA so that it can be stored until it is needed the next week. The absorbance values will be recorded into the Excel spreadsheet. Additional instructions found in the Excel spreadsheet will be followed in order to analyze the data. Read More