2. Connect the SpectroVis Plus spectrometer to the USB port of the LabQuest2. a. The LabQuest will automatically go into full spectrum mode. b. Under the 1st Sensor tab, click under Sensors, Calibrate, USB: Spectrometer and allow the spectrometer to warmup for 90 seconds. c. Then, place a blank liquid in a cuvette to the half full mark. Place the cuvette in the spectrometer. Be sure that the smooth sided windows are oriented in the light path. d. Click Finish Calibration on the screen after warmup is done counting down. e. Press Ok when complete to return to the main screen. f. Press Play to start reading a spectrum. g. With the blank cuvette still in place, the spectrum should be close to a flat line. 3. Empty the cuvette you used for the above blank and pour in one of the colored solutions. Make sure the LabQuest2 is playing and collecting spectra in real-time. Place the cuvette in the SpectroVis slot and allow a few seconds to pass while the spectrum stabilizes. 4. Draw the spectrum below. Be sure to title the drawn spectrum with the color of the solution. Also, subtitle the spectrum with the minimum wavelength. The minimum is not absorbed but emitted by the solution. Page 59 of 77
Spectroscopy 5. Repeat Step 4 for every colored solution provided. If you need additional plots then hand draw them on separate paper and include them with your report. Page 60 of 77
Lab 12 PROCEDURE, Part 2: 1. Obtain and wear goggles. Work in only pairs. 2. Place the 0.5 M CuSO 4 solution in a cuvette and measure it. Press Play to obtain the full spectrum. Press the Stop button. Under the 2nd Graph tab, click on the maximum non- squiggly absorbance. Write the absorbance maximum here: Absorbance Maximum (in nm): 3. Under the 3rd XY tab, record the absorbance from the XY data table at the above maximum wavelength in the below table. 4. Using a 10 mL graduated cylinder, dilute 1 mL of the 0.5 M CuSO 4 to 2 mL using distilled water. Use a dropper to be as precise as possible. Collect the spectra of this solution and record the absorbance at the above maximum wavelength in the below table. 5. Dilute the 0.25 M solution from the previous Step 4 in the same way as in Step 4. Repeat the dilutions and measure those absorbances at the maximum wavelength to complete the following table. These are called serial dilutions. Molarity Absorbance 0.50 0.25 0.13 0.063 0.031 0.016 0.0078 Unknown 6. Measure the absorbance of the unknown solution and record it above. 7. Disconnect the SpectroVis from the LabQuest and click File, New. a. Under the 3rd XY tab, manually enter the above Molarity (X) versus Absorbance (Y) data for the known concentrations. b. Under the 2nd Graph tab, click on Analyze, Curve Fit, Absorbance (Y). Choose Linear under Fit Equation. Record the slope and intercept of the line and write the full equation of a line below: A = ___________________ c + ______________________ Page 61 of 77
Spectroscopy 8. Using algebra, solve the above equation for c and report the unknown concentration for the unknown solution using the measured absorbance.
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