Name: Section: Date: Experiment #9 Pre-Lab Questions of tortdilo se o ob 1. (a) Write a statement of Beer's Law. (b) Write a statement of Lambert's Law. 0 1 ono com bolo towie soitain balt ei meet es adtad bluro) p 2. If 2.0 mL of distilled water is added to 3.0 mL of a 0.150 M solution of CoCl2, what is the concentration of the resulting solution? Show your work. cielo loro il gol dit bardzo blowid 30 Sal 3. What is the color of a solution containing a compound that absorbs most strongly at 550 nm? Experiment 9 155 4. (a) What is a calibration curve? (b) Why do we use a calibration curve to determine the concentration of our unknown? sto 5. A colored sample with a concentration of 0.160 M has an absorbance of 0.80 in a 1.0 cm path length cuvette. (a) What would be the absorbance expected if the sample is diluted to a concentration of 0.040 M? Explain. Oslo 0. boligblom OCH o od Yao lo (b) What would be the absorbance expected if the path length of the original solution is decreased to 0.10 cm? Explain. Experiment #9 Problems 1. By Least Squares Analysis, determine the slope of your calibration curve for CoCl2: Show all your work and remember to include proper units for your slope. 2. What weight of solid CoCl, would you need to prepare 50.0 mL of 0.150 M CoCl2 solution? 3. If 1.5 mL of distilled water is added to 3.5 mL of 0.300 M CoCl, solution, what is the concentration of the resulting solution? 160 Spectrophotometry 4. A 0.100 M sample of NiSO4 gave an absorbance of 0.60 at 600 nm in a 1 cm cuvette. What is the nickel concentration of a solution giving an absorbance of 0.20 in the same cuvette at the same wavelength? Show calculations. (a) How are percent transmittance and absorbance related mathematically? 5. (6) What would be the absorbance of a sample with 20 % transmittance? Show calculations. Experiment 9 161 ANALYSIS CO Name: Section: Date: A VISIBLE SPECTRA (nm) Color 1 (nm) ^ (nm) Color 425 Violet Color Green 500 575 Yellow 8 450 Blue 525 600 orange 475 Blue Green Green 550 ABSORBANCE AS A FUNCTION OF COCI, CONCENTRATION AT 500nm Sample Concentration Absorbance #1 #2 #3 #4 0.150M 0.120M o.ogom 0.075M 0.06 M 0.045M 0.630 M 0.00M -ault 1.0550 #e o 125 25 0.903 0.762 too oftes 0.594 eso 0.476 0.355 relt to.244 Tors 0.159 Totoo 2.5 #5 #6 #7 \ #8 #9 9 2М oto Experiment 9 157
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