Copper Iodide Lab Report

Abstract

The aim of the experiment was to obtain pure Copper (I) Iodide (CuI) and to determine the mass percentage of copper in the purified CuI sample .Crude CuI was obtained by redox reaction of Copper Sulphate pentahydrate (CuSO4.5H¬¬2O) and Potassium Iodide. The crude CuI was further purified to obtain pure CuI. Standard solutions with known concentrations of Cu2+ ions, ranging from 0 to 0.0032g/L was prepared and the absorbance values were obtained via UV-VIS spectroscopy. A graph of absorbance value against the concentration of Cu2+ was plotted to measure the concentration of Cu2+ in the pure CuI. It was found through UV-vis spectroscopy, the experimental yield of purified CuI of 52.5%, had an absorbance value of 0.7369A and from the

The use of CuI ranges from being used as catalysts for reactions such as Sonogashira coupling reactions, for mercury testing or detection, cloud seeding and even for organic synthesis.

Most copper salts are slightly soluble in water and are highly unstable and Copper (I) ions in solution and would disproportionate to give Copper (II) ions and a precipitate of copper. The disproportionate reaction is:

2Cu+⇌ Cu2+ + Cu

Hence to prevent disproportionation from occurring, our objective was to synthesize CuI as it is insoluble and later determine the mass percentage of the copper, the primary objective, in the CuI sample.

For this experiment, to obtain CuI, we used a redox reaction of Copper Sulphate pentahydrate (CuSO4.5H¬¬2O) and Potassium Iodide. The Copper ions will react with Iodine ions to form CuI and I2 in a two-step reaction below:

2 Cu2+ (aq) + 2 I- (aq)  2 Cu- (aq) + I2 (s) ----1

2Cu+(aq) + 2I-(aq)  CuI(s)

CuI2 precipitate would decompose immediately to from CuI. Excess Na2S2O3 is added to react with Iodine to form I- ions which can be filtered out via suction filtration, the residue being CuI.

I2(s) + 2 Na2S2O3 (aq) 2 NaI (aq) + Na2S4O6

3.0 ml of 0.1% cuprizone was added and the solution was diluted with deionised water in a 25ml volumetric flask. The solution was labelled solution D and allowed to stand for 10min. The above steps were repeated with varying amount of stock solution ranging from 0ml, 3.0ml and 6.0ml and labelled solution A-C with ascending order of stock solution used.

Part 4: Spectrophotometric analysis of purified