Heaven Lin and Forest Lin
W.M. Keck Science Department, Claremont McKenna, Pitzer, and Scripps Colleges
925 N. Mills Avenue, Claremont, California 91711
Through using the spectrometer and titrations, the amount of the coordination compound, pentaaminechloridocobalt (III) chloride, was determined through a synthesis through an oxidation reduction of cobalt (II) chloride hexahydrate (CoCl2·6H2O) and a reaction of the product with ammonium chloride (NH4Cl) and ammonia (NH3). Through iodometric and spectrophotometric analysis, the percent cobalt was then found in the samples of pentaaminechloridocobalt. When looking at the iodometric analysis, there was a mean amount of 26.29% cobalt with an average deviation of ± 1.00%. When looking at the spectrophotometric analysis, there was a mean amount of 15.30% cobalt with an average deviation of ± 2.00%. With a theoretical yield of 23.50%, the iodometric analysis proved to be more accurate than the spectrophotometric analysis.
Keywords: Pentaaminchloridocobalt, iodometric analysis, spectrophotometric analysis
Introduction In chemistry, the study of transition metals allows the scientist to witness coordination complexes form with ligands, such as a non-metal atom (electron donor). Another way of looking at the electron donor is as a Lewis base that is a compound or ionic molecule that can donate an electron pair to an acceptor molecule. In this experiment, the pentaamminechloridocobalt(III) ([Co (NH3)5Cl]2+) is synthesized and then analyzed through an iodometric and a spectrophotometric analysis to find the amount of cobalt in the solution. Through an oxidation reaction of synthesizing pentaaminechloridocobalt (III) chloride with cobalt (II) hexahydrate and hydrogen peroxide, and then reacting the product with ammonium chloride and ammonia, complexes are formed with the chloride and ammonia ions. The balanced