8. 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. e.Select OK. The graph should indicate a direct relationship between absorbance and concentration, a relationship known as Beer’s law. Record the linear fit equation in your data table. IMPORTANT : Don’t change anything in the LabQuest App. You will use the best-fit line equation in Part II.
The Determination of an Equilibrium Constant Advanced Chemistry with Vernier 10 - 5 Part II Prepare and Test Equilibrium Systems 9. Label three new small beakers A-C. Prepare the solutions according to the chart below. Use 10.0 mL graduated cylinders to measure the solutions. Mix each solution thoroughly. Note: You are using 0.0020 M Fe(NO3)3in this test. Beaker 0.0020 M Fe(NO3)(mL) 0.0020 M SCN–(mL) H2O (mL) A 3.00 3.00 4.00 B 3.00 4.00 3.00 C 3.00 5.00 2.00 10. Collect absorbance-concentration data for the three beakers of equilibrium mixtures. a.Using the solution in Beaker A, rinse the cuvette twice with ~1 mL amounts and then fill it 3/4 full. Wipe the outside with a tissue and place the cuvette in the device (Spectrometer or Colorimeter.) b.Write down, in your data table, the absorbance of the sample in Beaker A. c.Trace along the linear regression equation to find the FeSCN2+concentration for the sample in Beaker A. Write down the concentration in your data table. d.Discard the cuvette contents as directed. Rinse and fill the cuvette with the solution in Beaker B and place it in the device. After the reading stabilizes, write down the absorbance in your data table and use the Interpolate function to determine the concentration of the sample. e.Repeat Step d for the mixtures in Beaker C. 3
LabQuest 10 10 - 6 Advanced Chemistry with Vernier DATA TABLE Part I Temperature: °C Beaker [FeSCN 2+ ] Absorbance 1 2 3 4 Linear Regression Equation Part II Beaker Absorbance [FeSCN 2+ ] at equilibrium A B C