Lab 3 - Solutions and Spectroscopy

Be careful while doing this the pipets may be tricky

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Unformatted text preview: Solution 1 into a test tube and record your volumes in Data Table A. • Be careful while doing this, the pipets may be tricky to handle at first. • Record volumes to 0.01 mL with some uncertainty in the last digit. 6 Stopper the test tube and mix the solution well by inverting a couple of times. 7 To condition your vial, carefully pour a small amount of the solution you just prepared into a vial and pour it out to waste. 8 Refill the vial with solution and take an absorbance spectrum. Identify the wavelength of maximum absorbance near 600 nm. Record the wavelength and absorbance at this wavelength in Data Table A. Absorbance values are reported to the 0.001. For all remaining absorbance measurements in this experiment, be sure to use the same wavelength you have identified as the maximum. 9 Record the concentration of Cu2+ in Solution 1 in Data Table A. 10 Retain the sample in the vial until you have completed your calibration plot. Students often choose to label a sheet of paper with positions 1, 2, 3 and 4, placing each vial on the appropriate position. 11 Following steps 5 - 10, prepare Solutions 2 - 4, measure their absorbances and calculate the Cu2+ concentration in each. Record these in Data Table A. Do not close the MicroLab file, as this calibration curve will be used to determine the concentrations in Part B. 12 www.webassig encheml1/lab_3/manual.html 5/7 4/15/13 Lab 3 - Solutions and Spectr oscopy The MicroLab software will plot the absorbance of the Cu2+ solutions that you made as a function of their concentrations. The trendline and R2 value are displayed. If your plot is linear with an R2 value of 0.9 or greater, continue the experiment. If your R2 value is low, consult with your lab instructor. 13 Safely dispose of the calibration solutions in your copper waste beaker. 14 Obtain a couple of milliliters of unknown solution and record the number of your solution in Data Table A. 15 Condition a vial with the unknown Cu2+ solution and refill with unknown Cu2+ solution. Measure the absorbance of the unknown Cu2+ solution and record it in Data Table A. Part B: Preparation of a Copper(II) Ion Solution from Solid CuSO4 · 5 H2O 1 Carefully weigh the desired amount of CuSO4 · 5 H2O on a weighing paper or in a small beaker as shown in the Using an Analytical Balance video under Instructional Videos and as described in the Analytical Balance section of the Lab Equipment of this lab manual. Record the exact am...
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This document was uploaded on 01/22/2014.

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