Analyte R exhibits a maximum visible absorption at 530 nm
CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
Analyte R exhibits a maximum visible absorption at 530 nm, where its molar absorptivity is reported as 4.8 × 10⁴ L mol⁻¹ cm⁻¹. At 550 nm the molar absorptivity is 12 % lower than the value at 530 nm. A technician inadvertently performs both the calibration and the analysis of an unknown sample at 550 nm but continues to use the molar absorptivity value reported for 530 nm. The cuvette path length is 1.00 cm, and the true concentration of the unknown sample is 3.2 × 10⁻⁶ mol L⁻¹.
Answer the following questions.
(a) Calculate the absorbance that is actually measured for the sample at 550 nm.
(b) Using the (incorrect) molar absorptivity value for 530 nm, determine the concentration that the technician will report.
(c) Compute the percent error in the reported concentration relative to the true concentration.
(d) Propose one procedural safeguard that laboratories could implement to prevent this specific type of wavelength-selection error in future analyses.