Cowbolt

CowboltFebruary 25, 2015

ExperimentalThe experiment was carried out mostly using the procedures found in the lab manual4. During the synthesis of the two compounds, all volumes outlined in the lab manual were doubled.

Synthesis of Chloropentaaminecobalt(III) Chloride ([Co(NH3)5Cl]Cl2)To begin the experiment, (x) grams of hydrated cobalt chloride (CoCl2H2O) and (x) grams of NH4Cl were placed in a 250 mL Erlenmeyer flask along with 30 mL of concentrated aqueous ammonia (Equation A.1). The mixture was swirled for a few minutes and a stirring rod was used to break up the larger crystals in order to ensure the completion of the reaction. Next, 15 mL of 30% hydrogen peroxide (H2O2) was added dropwise to the previous solution with continuous swirling (Equation A.2). This mixture was then placed in a room-temperature water bath. The temperature of the water bath was raised to (x) degrees for (x) minutes. The flask was frequently swirled in order to mix the unreacted material with the rest of the solution. After the flask finished heating, it was cooled in an ice bath. Once the solution reached (x) degrees, 30 mL of 12 M HCl was added dropwise while the flask was still in the ice bath. Once the solution reached (x) degrees, the solid was filtered out with a Buchner funnel, washed with 2 portions of 10 mL of 6M HCl and 2 portions of 10 mL of acetone, and allowed to suction-dry for 10 minutes. This solid was then dissolved in a beaker with 300 mL of DI water and filtered with a clean Buchner funnel. The filtrate was moved to a 250 mL Erlenmeyer flask and warmed to (x) degrees. The flask was transferred back into an ice bath while 90 mL of 12 M HCl was added over (x) minutes while swirling (Equation A.3). The solution was warmed to (x) degrees and the temperature was maintained for (x) minutes. The final solution was cooled to (x) degrees using an ice bath. The product was filtered out using a vacuum filtration apparatus into a sintered glass crucible weighing (x). This product was washed with two 10 mL portions of 6 M HCl and dried with 10 mL of acetone. The suction was continued for (x) minutes. The glass crucible was stored in a desiccator until the following week.Synthesis of Compound W (x) grams of [Co(NH3)5Cl]Cl2 were initially weighed out and combined with 90 mL of 5% aqueous ammonia in a 250 mL Erlenmeyer flask (Equation A.4). The mixture was slowly heated in a water bath with frequent swirling, taking (x) minutes to heat to (x) degrees Celsius. The solution was left at this temperature for (x) minutes after the solid completely dissolved. This solution was immediately filtered through a Buchner funnel, and the filtrate collected. The filtrate was cooled to (x) degrees in an ice bath, then concentrated HCl was added dropwise until fog no longer formed over the solution, and red precipitate stopped forming (Equation A.5). (x) mL of HCl was used. The solution was cooled to (x) degrees Celsius. The precipitate was filtered into a (x) gram sintered glass crucible and washed with 3 portions of 10 mL of 95% ethanol. The product was placed into a refrigerator and the final mass of both the crucible and the precipitate was taken.Determination of Molar Mass of Cobalt(III) CompoundThis test used 0.151 grams of the unknown cobalt compound and 0.151 grams of [Co(NH3)5Cl]Cl2. These were placed in separate, labeled 150 mL Erlenmeyer flasks. Flask 1 contained the unknown cobalt compound while flask 2 contained [Co(NH3)5Cl]Cl2.Two boiling beads and 10 mL of 3M H2SO4 were added to each flask (Equation). 0.2008 and 0.1995 grams of oxalic acid were added to flasks 1 and 2, respectively. Each solution was boiled in the fume hood until foaming occurred. Once the foaming ended, the flasks were cooled on the bench top until the SO3 fumes cleared. 0.1996 and 0.2023 grams of oxalic acid were then added to flasks 1 and 2. The walls of the flasks were rinsed with DI water. These solutions were boiled once again until the foaming ended. After the solutions were cooled on the bench top, 50 mL of DI water was used to rinse the walls of each flask. The flasks were reheated to a boil and swirled to dissolve any remaining crystals. Each solution was diluted to 100 mL and allowed to cool to room temperature.Next, the solution in flask 1 was transferred to a 250 mL volumetric flask and diluted to the mark with DI water. The solution was mixed and 10 mL was transferred to a 100 mL volumetric flask. 10 mL of 50% ammonium thiocyanate (NH4SCN) and 50% ethanol was also added to the 100 mL flask, which was then diluted with water to volume (Equation). After mixing by inversion, the absorbance of the solution at a 621 nm wavelength was measured using a Spec 20. A mixture of 2.0 mL of 50% NH4SCN, 8.0 mL of water, and 10.0 mL of 95% ethanol was used as the blank. This procedure was also used to measure the absorbance of flask 2, using the same quantities and glassware. Determination of the Non-Ammonia LigandsFor this test, 0.204 g of [Co(NH3)5Cl]Cl2 and .202 g of compound W was used. These samples were placed in separate 100 mL volumetric flasks which were filled to volume with DI water. After mixing, the known and unknown samples were placed into separate curvettes. A fiber-optic UV-Vis spectrophotometer was used to measure the visible absorbance (360-700 nm wavelength) of each solution. The spectrophotometer was blanked using DI water.Determination of the Charge of the Complex Ion by Ion ExchangeThis experiment uses an ion exchange column packed with 10-15 cm of Dowex 50W-X8 cation exchange resin. This was rinsed with three portions of 25 mL DI water. The column was inspected to ensure its quality.0.3022 g of compound W was placed into a 250 mL with 100 mL of DI water. This solution was run through the ion exchange column at approximately 10 mL per minute and collected in a 250 mL Erlenmeyer flask. After the solution was run through, the column was rinsed with 3 25 mL portions of DI water, which was collected in the same flask. This was titrated using our prepared NaOH solution, and the volume of NaOH used was recorded.Determination of the Number of Ammonia LigandsThe distillation apparatus was first assembled with 50.0 mL of the HCl solution. A solution of .184 g of compound W was dissolved in 100 mL of DI water in the flask that was to be heated. Two boiling chips and 10 mL of 19 M NaOH were added to this flask and the stopper was replaced. We swirled the flask to mix the solution and slowly heated it up to a boil. The ice on top of the receiving flask was continuously replaced as it melted during the heating process. After 23 minutes and 16 seconds of boiling, the HCl solution was removed and the glass tube washed into the solution. This was brought to room temperature, and titrated with the .1 M NaOH solution using bromcresol green as the indicator. The volume of NaOH added was recorded.

Appendix ASynthesis of [Co(NH3)5Cl]Cl2A.1A.2A.3

Appendix ACompound M synthesis A4 A5 Molar Mass determination A6 A7 A8 A9 A10 A11 Determination of non-ammonia ligandA12 A13

Ion exchange column A14

A15 Determination of the number of ammonia ligandsA16 A17 A18 Titration of HCl solution with bubbled NH3A19 Titration of Effluents, NaOH standardization, and HCl standardization A20

References1. Meher, L.; Sagar, D.; Naik, S. Technical aspects of biodiesel production by transesterification a review. Renewable and Sustainable Energy Reviews, 2006, 10, 3.1. Fukuda, H.; Kondo, A.; Noda, H. Biodiesel fuel production by transesterification of oils. Journal of Bioscience and Bioengineering, 2001, 92, 5.1. Roy, C.; Lepage, G. Direct transesterification of all classes of lipids in a one-step reaction. Journal of Lipid Research, 1986, 27, 114.(4)An Introduction to Chemical Systems in the Laboratory. Department of Chemistry, University of Illinois, Urbana-Champaign. 2013.