Spectroscopy and a Calibration Curve Prepare a series of standard solutions of the colored compound with known concentrations by diluting the stock solution with distilled water. Use volumetric flasks to ensure accurate dilutions. Let's assume we have a stock solution of potassium permanganate (KMnO4) with a concentration of 0.100 M (molar). We will prepare five standard solutions with the following concentrations by diluting the stock solution with distilled water: 0.020 M 0.040 M 0.060 M 0.080 M 0.100 M Measure the absorbance of each standard solution at the wavelength of maximum absorbance (λmax) using the UV-Vis spectrophotometer. Record the absorbance values. For 0.020 M: Absorbance = 0.150 For 0.040 M: Absorbance = 0.290 For 0.060 M: Absorbance = 0.440 For 0.080 M: Absorbance = 0.580 For 0.100 M: Absorbance = 0.730 Plot a calibration curve by graphing the absorbance values (y-axis) against the corresponding concentrations (x-axis) of the standard solutions. Use a linear regression analysis to obtain the equation of the best-fit line. Measure the absorbance of the unknown solution at the same wavelength (λmax). Unknown Solution: Absorbance (unknown) = 0.510 Use the equation of the calibration curve to calculate the concentration of the unknown solution based on its absorbance. Quiz Questions: What is the purpose of preparing a calibration curve in this experiment? Based on the calibration curve you plotted, what is the equation of the best-fit line? (Provide the slope and y-intercept values.) Calculate the concentration of the unknown solution using the equation of the calibration curve. Show your calculations. How would the accuracy of the experiment be affected if the cuvettes were not properly cleaned before use? Why is it important to measure the absorbance of the solutions at the wavelength of maximum absorbance (λmax)?

Chemistry

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter1: Chemical Foundations

Section: Chapter Questions

Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...

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Spectroscopy and a Calibration Curve

Prepare a series of standard solutions of the colored compound with known concentrations by diluting the stock solution with distilled water. Use volumetric flasks to ensure accurate dilutions.

Let's assume we have a stock solution of potassium permanganate (KMnO4) with a concentration of 0.100 M (molar). We will prepare five standard solutions with the following concentrations by diluting the stock solution with distilled water:

0.020 M
0.040 M
0.060 M
0.080 M
0.100 M

Measure the absorbance of each standard solution at the wavelength of maximum absorbance (λmax) using the UV-Vis spectrophotometer. Record the absorbance values.

For 0.020 M: Absorbance = 0.150
For 0.040 M: Absorbance = 0.290
For 0.060 M: Absorbance = 0.440
For 0.080 M: Absorbance = 0.580
For 0.100 M: Absorbance = 0.730

Plot a calibration curve by graphing the absorbance values (y-axis) against the corresponding concentrations (x-axis) of the standard solutions. Use a linear regression analysis to obtain the equation of the best-fit line.

Measure the absorbance of the unknown solution at the same wavelength (λmax).

Unknown Solution: Absorbance (unknown) = 0.510

Use the equation of the calibration curve to calculate the concentration of the unknown solution based on its absorbance.

Quiz Questions:

What is the purpose of preparing a calibration curve in this experiment?
Based on the calibration curve you plotted, what is the equation of the best-fit line? (Provide the slope and y-intercept values.)
Calculate the concentration of the unknown solution using the equation of the calibration curve. Show your calculations.
How would the accuracy of the experiment be affected if the cuvettes were not properly cleaned before use?
Why is it important to measure the absorbance of the solutions at the wavelength of maximum absorbance (λmax)?

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