During an experiment to determine the concentration of a colored antioxidant in juice
CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
During an experiment to determine the concentration of a colored antioxidant in juice, a student accidentally touches the optical face of a 1.00cm cuvette. The smudge increases the apparent absorbance by 3.0% relative to a perfectly clean cuvette. The instrument records an absorbance of 0.672 for the smudged cuvette. At the measurement wavelength, the antioxidant’s molar absorptivity is 1.28×103L mol−1cm−1.
Use the data provided to answer the following questions.
(a) Using the recorded absorbance, calculate the concentration of the antioxidant that the student would report if the smudge were not noticed.
(b) Determine the true concentration that would have been obtained with a clean cuvette.
(c) Compute the percent error introduced by the smudge, relative to the true concentration.
(d) Describe two practical laboratory steps that should be taken to minimize this type of systematic error in future spectrophotometric measurements.