a. Empty the solution from the blank cuvette. Using the solution in Beaker 1, rinse the cuvette twice with ~1 mL amounts and then fill it 3/4 full. Wipe the outside with a tissue, place it in the Spectrometer. b. Start data collection. A full spectrum graph of the solution will be displayed. Stop data collection. The wavelength of maximum absorbance ( max) is automatically identified. c. Tap the Meter tab. On the Meter screen, tap Mode. Change the mode to Events with Entry. d. Enter the Name (Concentration) and Units (mol/L). Select OK. Colorimeter Users Only (Spectrometer users proceed to the Spectrometer section) 4. Connect the Colorimeter to LabQuest and choose New from the File menu. 5. Calibrate the Colorimeter. a. Place the blank in the cuvette slot of the Colorimeter and close the lid. b. Press the < or > buttons on the Colorimeter to set the wavelength to 470 nm. Press the CAL button on the Colorimeter. When the LED stops flashing, the calibration is complete. 6. Set up the data-collection mode. a. On the Meter screen, tap Mode. Change the mode to Events with Entry. b. Enter the Name (Concentration) and Units (mol/L). Select OK. c. Proceed directly to Step 7.
10 - 4 Advanced Chemistry with Vernier LabQuest 10 Both Colorimeter and Spectrometer Users 7. Collect absorbance-concentration data for the four standard solutions in Beakers 1-4. a. Start data collection. b. Empty and rinse the cuvette. Using the solution in Beaker 1, rinse the cuvette twice with ~1 mL amounts and then fill it 3/4 full. Wipe the outside with a tissue and place it in the device (Colorimeter or Spectrometer). Close the lid on the Colorimeter. c. When the value displayed on the screen has stabilized, tap Keep and enter the value for the concentration of FeSCN 2+ from your Pre-Lab calculations. Select OK. The absorbance and concentration values have now been saved for the first solution. d. Discard the cuvette contents as directed by your instructor. Using the solution in Beaker 2, rinse the cuvette twice with ~1 mL amounts, and then fill it 3/4 full. Place the cuvette in the device, wait for the value displayed on the screen to stabilize, and tap Keep. Enter the value for the concentration of FeSCN 2+ in Beaker 2, then select OK. e. Repeat the procedure for Beakers 3 and 4. Note: Wait until Step 10 to test the unknown. 8. Stop data collection. To examine the data pairs on the displayed graph, tap any data point. As you tap each data point, the absorbance and concentration values are displayed to the right of the graph. Record the absorbance and concentration data values in your data table. 9. Display a graph of absorbance vs. concentration with a linear regression curve. a. Choose Graph Options from the Graph menu. b. Select Autoscale from 0 and select OK. c. Choose Curve Fit from the Analyze menu. d. Select Linear as the Fit Equation. The linear-regression statistics for these two data columns are displayed for the equation in the form y = mx + b e. Select OK. The graph should indicate a direct relationship between absorbance and concentration, a relationship known as Beer’s law. The regression line should closely fit the five data points and pass through (or near) the origin of the graph. Record the linear fit
You've reached the end of your free preview.
Want to read all 6 pages?