Synthesis and Characterization of Cobalt III Coordination Compounds Pre Lab Part 4 Cobalt Questions to Consider 1 What data do you need to gather in order to determine the formula of your unknown In order to determine the formula for the unknown it is necessary to find the molar mass of the compound which can be determined by spectroscopy Comparing the absorbance values of the solution containing the unknown compounds the moles of cobalt can be determined Since the mass is known of the unknown is known molar mass can be determined of the unknown The number of non ammonia ligands is necessary This can be done by using UV vis fiber optics By comparing maxima spectra the relative field strength can be deduced to find the unknown ligand present The charge of the complex ion is necessary which can be found by ion ion exchange which will be discussed in the next answer The determination of the number of ammonia ligands is necessary This is done by calculating number of moles of NH3 released by a known mass of unknown into HCl A combination of all of these things is necessary to find the formula for the unknown compound and finally the identification of counter ions is necessary This data can be used to determine the counter ions 2 Briefly describe how you will find the overall charge of the complex ion The charge can be found from the Dowex 50W X8 exchange This is then used to run the solution through and perform an ion exchange in the process The process for finding the overall charge of the complex ion is done by knowing the moles of H produced by a given amount of unknown being passed onto the ion exchange column The charge can then be calculated on the complex ion in the unknown by comparing the amount of moles of acid produced to moles of unknown run through the column 3 How do you use Beer s Law in this lab You find the absorbance in the solutions from the spectrophotometer Beer s law states A bc Where epsilon is the extinction constant b is the path length and c is the concentration The ratio of the absorbance s can be compared since the extinction constant and the path length stay the same therefore beer s law can be used to find the absorbance s and then concentrations and then molar mass 4 What is the initial step for the synthesis of all compounds Why is this Aqueous ammonia was mixed with all of the compounds as the initial step in the process This was done because all of the unknown and known compounds have ammonia ligands in them This came from the initial mixing of the aqueous ammonia 5 In determining the number of ammonia ligands you must be careful when you turn off the heat Why If the heat is turned off too soon the HCl solution will be drawn back into the solution and ruin the experiment If it is ruined it must be repeated This is bolded in the lab notebook1 so I assume this is pretty important References 1 University of Illinois at Urbana Champaign An introduction to Chemical Systems in the Laboratory Chem 203 205 2013 2014 ed Hayden McNeil Plymouth MI 2013