Spectroscopy and Distilled Water
1. KMnO4 was weigh accurately to nearest mg. The reading was recorded. The solid transfer to a 100ml volumetric flask using funnel. 2. The solid was dissolved with distilled water. The flask was shaken after using stopper. Distilled water was added to the mark ,the dropper was used when reaching the last drop. The flask was stopped using stopper and shake several time to give the solution homogenize. 3. The stock was pour into a beaker. The beaker was labelled as 100 ppm. 4. 5. 00 ml of the stock was pipet and diluted with distilled water in a 100ml volumetric flask.
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5. The solution was transfer to a beaker and labelled as 5 ppm. 6. Steps 4 was repeated using 10ml, 15ml, and 20ml. 7. The beaker was labelled as 10ppm, 15ppm, and 20ppm respectively. B. Preparation of the unknown 1. The unknown solution was pipet between 5. 00ml to 20. 00ml of the stock KMnO4 solution and was diluted with distilled water in a 100ml volumetric flask. 2. The solution was transfer to a beaker and labelled as unknown solution. C. Determination of absorption maximum 1. Distilled water was used as blank for determination of absorption maximum.
2. The blank solution was put at the end of the tips contain quartz to calculate the absorption maximum. 3. The result of absorption maximum from the graph was printed. 4. Absorption maximum will be used to determine the unknown concentration. D. Operation of the UV-VIS spectrophotometer 1. Cary win UV was selected and setup like the machine needed before run the experiment. 2. The machine need to adjust the y-mode is min=0 and max=1 ,then the x-mode is 800-400nm. 3. The machine was set to fast scan control and the baseline correction function was selected.
4. Finally all the setup was auto store by clicked at the storage on. 5. The ‘BLANK’ in the test tube was touched the device contain quartz until more than the marked line and the baseline was clicked. 6. After that, the ‘BLANK’ was removed and another test tube contain 5ppm was touch the device until more than the marked line. 7. The start icon was clicked for the measurement. E. Determination of the unknown concentration 1. The concentration icon was clicked. 2. The software was setup the maximum wavelength from the steps from D. 3.
3 replicated were selected 4. The calibration standard unit was set to (mg/L) and the number of the standard sample also was setup. 5. The fit type was selected to liner direct. 6. At the sample icon, the number of the samples was selected and the unknown was key in. 7. The storage on was set at the auto store icon. 8. The ‘BLANK’ solution was touch the device until the marked line and ‘ZERO’ was clicked. 9. The ‘BLANK’ was removed and change to other sample until the marked line. 10. The ‘start’ icon was clicked to start the measurement. QUESTION 1.
Why is glass not a suitable cell material for use in UV spectroscopy? Glass is not suitable cell material for use in UV spectroscopy because the glass only suitable for measure visible and glass will absorbed UV light ,for the conclusion the data will be affected. 2. State one advantage of using the UV-Vis spectrophotometer compared to a spectronic 20 for this analysis. UV-Vis spectrophotometer can measure UV and Visible but spectronic only can use to visible. CALCULATION DISCUSSION From the graph absorbance versus wavelength, the sample concentration use is 5ppm so the graph obtained is small.
The maximum wavelength get from the graph is 527. 0 because of the higher absorbance. There is some mistake occur during the preparation of the 5ppm and 10ppm that make the data get not accurate. The data from the graph show that 5ppm and 10ppm not on the linear line because problem in dilution of the sample. The dilution problem occur because during the measurement of the volume needed to dilute using the burette ,the eye not perpendicular on the burette that make the volume is more than 5ml and 10ml that make the graph show high absorbance at the 5ppm and 10ppm.
The correlation coefficient can be defined by measure the strength of the straight line or the relationship between the two or more variable in the data. The correlation coefficient denoted by r and the value between +1 and -1. From the data obtained, the correlation coefficient is 0. 99142. This value show that the graph not too straight line because the sample at 5ppm and 10ppm, the absorbance is high that make the graph of straight line not too strong. CONCLUSION As the conclusion, the maximum wavelength for the potassium permanganate is 527.
0nm. The concentration of the unknown solution of potassium permanganate is 15. 2ppm. The correlation coefficient is 0. 99142 . REFFERENCES 1. http://www. dmstat1. com/res/TheCorrelationCoefficientDefined. html 2. The basic instrumental analysis lab manual. CHM 260 LABORATORY REPORT EXPERIMENT NUMBER: 2 TITLE: UV-VISIBLE DETERMINATION OF AN UNKNOWN CONCENTRATION OF KMnO4 SOLUTION NAME: AHMAD IZZAT EMIR BIN ATAN STUDENT NO: 2010459882 LAB GROUP: A1 DATE OF REPORT SUBMISSION: 14/12/2011 LECTURER’S NAME: PN FARIDAH HANUM