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1.4 CHEMICAL SCIENCES
In deionised water, ascorbic acid (AH−), through oxidation by oxygen in the presence of copper(II), was found to degrade with zero-order kinetics. The magnitude of the reaction rate varied directly with the copper(II) concentration. At a higher pH (7.4), the same reaction was found to be pseudo-first order. Once again, the magnitude of the rate increased linearly with copper(II) concentration at a micromolar level. Dissolved oxygen levels, in excess AH− and trace copper(II), displayed similar kinetics under both conditions. Monitoring of either AH− levels or dissolved oxygen concentration was found to be a useful novel undergraduate practical laboratory for trace copper(II) determination. Students can measure the kinetics for standards and their unknown copper solution and quantitate the unknown copper.
Tobin Sean, Cassidy John, Kurian Kevin, Betts Anthony (2022) Analysis of copper(II) using the ascorbate/oxygen system – a valuable undergraduate resource. Australian Journal of Chemistry 75, 835-838. DOI: 10.1071/CH22164