Copper Iodide

Experiment 2: Preparation and Spectrophotometric Analysis of Copper(I) Iodide

Abstract:
This experiment aims to determine the concentration of “Purified CuI” sample. Crude CuI is obtained by reacting CuSO4.5H2O with KI and Na2S2O3 in de-ionized water. A series of decanting and centrifugation is carried out to extract the crude CuI. Crude CuI was later purified by dissolving it in hot KI solution. The solution was later transferred into de-ionized water and placed in an ice bath to allow for re-precipitation of “purified CuI” to settle. This is to ease the process of decanting and centrifugation carried out later. The concentration of “purified CuI” was determined by first diluting a solution of “purified CuI” twice, then carrying out UV-Vis

2ml of 10% ammonium citrate was added to each beaker. The pH was then adjusted to 8.5 by adding 10 drops of 5M NH4OH(aq) to each beaker. 3ml of 0.1% cuprizone was added to each beaker. The four solutions were then transferred to 25ml volumetric flasks. The beakers were washed with de-ionized water, and the washings were combined with the solutions in the 25ml volumetric flask. De-ionized water was then added to make up the 25ml standard solution A to D. Spectrophotometric analysis was then carried out on the four standard solutions. The absorbance vaule at 600nm was recorded for each standard solution. These data were used to obtain the calibration

Not enough time was given for the precipitate to settle in the beaker, hence when the supernatant is removed; there is a large amount of product lost. This is especially so in step 25, because a large amount of solvent is decanted. It will require much longer than the given time of 10 minutes to allow most of the precipitate to settle at the base of the beaker. Hence instead of decanting the mixture, centrifugation can be used to remove the solution instead. The amount of product lost will be significantly lower by carrying out this process. This is because when centrifugation is carried out, the precipitate will be clustered at the base of the centrifugation tube and when the supernatant is poured away, little to no precipitate would be lost. This can be known by seeing that the supernatant of the centrifuge tube after centrifugation is clear and there is a lack of suspension in the