Posted on Feb 08 2013 by Sam Priest, Natalie Williamson

Ion exchange chromatography is a critical analytical technique routinely used for the separation of compounds based on their charge for a wide range of purposes. This experiment provides students with experience executing the technique, and also builds knowledge of the theory behind how the process works by using ion exchange columns to identify products of hydrolysed copper complexes. In so doing students are also exposed to and gain an understanding of the relationships between the strength of reaction conditions and products produced as a consequence. /span>

Initially, students are asked to identify three complex salts from a mixture by charge and colour using an ion exchange column. Once they have developed a level of confidence in the process of identification, students then expose carbanato bisethylenediamine cobalt (III) chloride to varying conditions of hydrolysis; dilute hydrochloric acid, concentrated hydrochloric acid and hot concentrated hydrochloric acid; and are asked to identify the different species produced in each case. Hydrolysis removes the carbonato ligand from the complex, and students can expect to see the two coordination sites replaced by water or chloride ions to give diaquo, aquochloro and/or dichloro bisethylenediamine cobalt (III) chloride as products, the presence of each being dependant on the availability of chloride ions in comparison to water in each of the three reaction conditions. Students are expected to identify which species are present in each case based on characteristic colour and charge, and answer a series of questions concerning identification methods and reasons the products differ in each case.

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