A team of researchers collected the following absorbance data for solutions of…
CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
A team of researchers collected the following absorbance data for solutions of compound X in a 1.20 cm quartz cuvette at a single wavelength.
Concentration (µM)
Absorbance
2.00
0.122
4.00
0.238
6.00
0.365
8.00
0.486
10.00
0.600
12.00
0.705
An additional unknown sample of compound X gave an absorbance of 0.415 under identical conditions.
(a) Using an appropriate linear regression technique, determine the numerical values of the slope and intercept of the best-fit line for the standards.
(b) From the slope obtained in part (a), calculate the molar absorptivity of compound X, reporting the value in L mol⁻¹ cm⁻¹.
(c) Use the calibration line to determine the concentration of the unknown sample in micromoles per liter.
(d) Examine the residuals (difference between observed and predicted absorbance) implied by your regression in part (a). Discuss whether the Beer–Lambert relationship appears to hold across the entire concentration range tested and justify your conclusion.