Synthesis and Characterization of Cobalt III Coordination Compounds Pre Lab Part 3 Procedure Determination of the Molar Mass of the Compound 1 For a detailed list of the procedure look to the lab manual1 2 Using an analytical balance weigh out around 15g of your standard Compound J And the unknown Compound M and place in separate labeled 250mL Erlenmeyer Flasks 3 To each flask add 2g of carefully measured oxalic acid two boiling beads and 10mL of 3M H2SO4 then boil the solution in a fume hood a Keep the level in the bottom of the flask even until the foaming from the oxalic acid has dwindled b Place the flasks in da hood to cool c When the fumes of SO3 have subsided add 2g of oxalic acid to each flask and rinse with a small portion of DI water 4 Bring the solution to a boil and heat until foam moderates The solution should look lavender 5 Cool in da hood Once the SO3 fumes have cleared use 50mL of DI water to rinse the inside walls of the flask Reheat the flask to boiling and swirl the crystals until they dissolve 6 Dilute each solution with 100 mL of DI water and allow to cool to room temperature 7 Transfer the solution to a 250 mL volumetric flask and dilute to the mark a Mix well then pipet 10 mL of the solution into an 100 mL volumetric flask b Add 10 mL of 50 NH4SCN and 50mL of 95 ethanol dilute to volume with DI water The solution should be blue c Mix by inversion like an Orangina d Place in a clean dry 400 mL beaker labeled standard Co SCN 42 and cover parafilm e The unknown solution should be treated the same way and labeled unknown 8 Turn on computer 15 minutes ago and in a small beaker mix 2 0 mL of 50 NH4SCN 8 mL of DI H2O and 10 mL of 95 ethanol for use as blank Set to 621 nm Determination of the Non Ammonia Ligands 1 Weigh 2g of compound J and 2g of M into separate 100 mL volumetric flasks and fill each one to the mark with DI water 2 Add 2 or 3 drops of 3 M H2SO4 to the solution to prevent decomposition 3 Fill cuvettes with the known and unknown solution 4 Using fiber optic UV Vis measure absorption spectrum of each solution from 360 nm to 700 nm and use DI water as the blank a ID peaks of each spectrum b Pick up infrared spectra from TA Determination of the Charge of the Complex Ion by Ion Exchange 1 Rinse the Dowex 50W X8 with three portions of 25 mL of DI water It is essential that the level of water in the column a If there are air bubbles do not use column b Be sure that the media has at least 1 3 of unused yellow media c Rinsing is complete when pH of water entering is the same as water leaving If not repeat the rinsing process 2 Weigh out approximately 3g of unknown and the standard compound Compounds M and J 3 Place in separate 250mL beakers Dissolve sample in 100 mL of DI water 4 Immediately run the unknown solution through the column at a rate of 10 mL per minute 5 Collect this effluent in a clean 250 mL flask 6 When the level of the solution approaches the top of the resin rinse the column with there portions of 25 mL of DI water 7 Repeat for standard compound collecting effluent in a clean 250mL flask a Check pH before running standard b Don t let column run dry 8 Calculate the concentration of the NaOH by titrating the effluent from the standard compound using phenolphthalein 9 Titrate the unknown with the same indicator and standardized NaOH 10 Calculate the charge Determination of the number of ammonia ligands 1 Standardize the HCl using the Standardized NaOH using phenolphthalein as indicator 2 Assemble the distillation apparatus shown in figure 8 41 a The receiver consists of a 250 mL Erlenmeyer flask containing exactly 50 0 mL of standardized HCl solution b Be very precise and use a volumetric pipet In a 1 liter beaker containing as much ice as possible surrounding it 3 Basically refer to lab manual for setup Attach two Erlenmeyer flasks one with heat underneath the other in the beaker connected by tubing with a beaker under the one in ice Heat the one on the heater 4 Be sure the glass tubing is not under and torsional strain 5 Weigh out 15 2 g of the unknown compound Transfer the sample to the 500mL flask and dissolve in 100 mL of DI water 6 Add 2 boiling chips and 10mL of 19 M NaOH 7 Quickly replace the stopper and keep the other end of the tube at the bottom of the HCL 8 Swirl the mux taking care not to disturb the position of the tube of HCl 9 Seal the receiving flask with foil to prevent gas from escaping 10 Be sure that the receiving flask is covered with ice 11 Be sure that it is cold to ensure that no ammonia gas escapes 12 Replace ice as needed and maintain a pile of ice on top of the flask at all times 13 Heat the basic solution containing the unknown compound M the boiling point but not too vigorously Starting at about 250 C on the hotplate a Boil slowly to ensure it does not gas is not forced to fast so that HCL can not absorb it b I am writing this on the b section because I have nothing else to say about this particular thing and it needs have two bullets underneath in order to be correct in the grammatical sense 14 Boil for 20 25 minutes but do not boil all of the water 15 Remove tube from HCl before you turn off the hotplate too soon it will be drawn back in and ruin the experiment 16 Wash the glass tubing into the HCl solution and bring it to room temperature 17 Titrate the solution with standardized 1 M NaOH from before 18 Use Bromcresol green The endpoint should be green If blue it was oershot if yellow continue 19 Clean flask by rinsing with water then boiling 20 mL of 3 M H2SO4 to dissolve cobalt stain Table of Reagents 1 Reagent Molar Mass g mol Density g mL Melting Point C Boiling Point C Hazards Co SCN 42 151 10 3 1 N A N A Hazardous if you intake it But it will be a fun trip to the hospital Dowex 50W X8 N A 1 7 N A N A 1M NaOH 40 1 54 0 100 Phenolphthalein 318 32 1 28 114 1 78 5 19 M NaOH 40 1 54 10 6 110 144 698 02 79 225 NA Density g mL Melting Point C Boiling Point C Bromcrescol Green No one knows what this is But you probably can t ingest it Just don t drink …