Analysis of Bleach and Copper: Experiment

Abstract

EXPERIMENT 6
Analysis of bleach and copper (ii) unknown
The objectives for this experiment are to standardize the sodium thiosulphate solution, todetermine the percentage of NaClO in sample and to determine the percentage of copper in anunknown copper sample.firstly, get the standardization molarity of the sodium thiosulphatesolution. Then, in part b, 10.0ml of the first bleach sample was pipette into the pre-weighed100ml volumetric above. The flask was reweighed and recorded. This will give the density of the bleach solution. The sample was diluted to the 100ml mark with distilled water. Then, it wasmixed well. The pipette was rinsed with distilled water followed with a little of the diluted bleach solution and a fresh 10.0ml aliquot was pipette into a 250ml conical flask. Next, 1.0 g of potassium iodide was added and it was swirled . then, 5.0ml of 6 M HCl was added to themixture. The sample was titrated with the standardized sodium thiosulphate solution until theamber iodine colour begins to fade to light yellow. 2 ml of the starch solution was added and thetitration was continued until the dark colour of the starch-iodine complex just disappears. Thetitration was repeated with two more 10.0ml aliquot of the diluted bleach solution. The analysiswith the second branch of bleach sample. About 0.3 g of copper (II) unknown was weighed intoa 250ml conical flask. The solid was dissolved with 35ml of 0.05 M sulphuric acid. 1.0 g of potassium iodide was added and it was swirled. Then, the mixture was titrated with thestandardized sodium thiosulphate solution until the amber color of the triiodide begins to fade.At this point 2 ml of starch solution was added. the titration was continued until the grey starch-iodine color disappears to produce a milky white-pinkish color that marks the end point. Thetitration was repeated with the two more samples. The percentage by mass of copper wascalculated. The experiment is very important because it gives the idea of oxidation and reductionat the same time it views a clear about iodometric reaction. From the calculation, the percentageof the NaClO in Depex is 6.8% while in Clorox is 6.5 %. The percentage of copper in anunknown copper sample is 58.7%. this percentage shows that the unknown copper (II) is actuallycopper (II) chloride dehydrate