Synthesis and Characterization of Cobalt III Coordination Compounds Procedure Compound J 1 Under a hood in a 125 Erlenmeyer flask 4 5 grams of crushed CoCl2 6H2O 6 grams of NH4Cl and 15 mL of aqueous ammonia were mixed Pan balances were used to weigh out reagents The mixture was swirled for a few minutes allowing pink crystals to convert to orange crystals Note that a stirring rod was used to break up large prink crystals 2 While continuously swirling 7 5 mL of 30 H2O2 was added slowly dropwise Note that the unreacted solid was not washed down into the flask with the peroxide This would have reduced the yield 3 The mixture was placed in a water bath at room temperature Then the temperature was raised to between 55oC to 60oC Note that this temperature range was not exceeded The mixture was in the bath for 10 minutes While the mixture was in the bath it was swirled to mix the unreacted material with the bulk of the mixture Note a thermometer was not used to stir 4 The flask was cooled to near 0oC in an ice bath 5 While the flask was still in the ice bath 15 mL of 12M HCl was added slowly dropwise 6 The solution was re cooled to near 0oC 7 The solid was isolated by filtration with a B chner funnel 8 The solid was washed with 10mL of 6M HCl and dried with 10 mL of acetone 9 Suction was continued for 10 minutes 10 The solid and filter paper were transferred to a beaker containing 150 mL of deionized water 11 This beaker was then stirred to dissolve as much solid as possible 12 The contents were then filtered with a B chner funnel 13 In the hood the filtrate was transferred to a 250 mL Erlenmeyer flask 14 This flask was warmed to 60oC 15 Over a 9 minute period using an ice bath while swirling 45 mL of 12 M HCl was added 16 The solution was warmed to 80oC and held there while frequently swirling 17 Ice was used to cool the solution to about 20oC 18 The product was isolated using suction with a sintered glass crucible 19 The products were washed with two 10 mL portions of 6 M HCl and dried with 10 mL of acetone 20 The suction was continued until the product was dry 10 to 15 minutes Table of Reagents Chemical Formula Acetone CH3 2CO Ammonia aq NH3 Ammonium chloride Cobalt II chloride hexahydrate Hexaamminecobalt II chloride Hydrochloric acid Molar Mass g mol Density g mL 58 08 43 0458 Hazards Very flammable Eye irritant 0 791 Hazardous inhalant 0 89 Toxic Can cause severe skin burns 53 491 Irritant if inhaled or if 1 5274 in contact with skin CoCl2 6H2O 237 93 Irritates and possibly burns through all 1 924 routes of exposure CoCl2 NH3 267 48 1 71 Skin and eye irritant 36 46 Strong Acid Toxic 1 191 Highly Corrosive NH4Cl HCl Hydrogen peroxide H2O2 34 0147 Aggressive Oxidizer 1 11 Corrosive Water H20 34 0148 1 18 N A Questions to Consider 1 You need to know the number of moles of acid produced when you titrate the hydrogen solution with NaOH and the number of moles of compound used to determine the charge of the complex ion You have to determine the moles of cobalt used in our unknown and the original mass of the unknown to determine the molar mass of the unknown compound 2 Our aqueous solution of unknown compound is passed through Dowex 50W X8 ion exchange resin Sulfonic acid groups dissociate when passed through this resin This produces hydrogen ions and sulfonate which is bound to the resin Complex cations then are exchanged with Hydrogen ions to form a solution This solution is then rinsed out and titrated with NaOH This will allow us to determine the number of moles of acid produced The ratio of the number of moles of acid to the number of moles of compound used will be the charge of the complex ion 3 Beer s Law states Abs bc This equation says that Absorbance is equal to the molar extinction coefficient times the path length b times the concentration c This law is used in combination with comparison of the absorbance of the solutions with the known and unknown compounds to determine the number of moles of cobalt in our unknown solution This along with the mass of the unknown originally used allows us to determine the molar mass of the unknown compound 4 The initial step for synthesis for all compounds is to mix Xg of crushed CoCl2 6H2O with Xg of NH4Cl and XmL of concentrated aqueous ammonia in a Erlenmeyer flask This converts the hexaaquacobalt II chloride to hexaaminecobalt II chloride 5 You have to be sure to remove the tube from the hot plate first or else the HCl solution will shoot back into the 500mL flask The same result happens if the temperature of the hot plate is reduce to reduce the rate of boiling This ruins your experiment You have to be careful when you turn off the heat as to not ruin your experiment