Standards of a textile dye were prepared in 0.500 cm path-length cuvettes
CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
Standards of a textile dye were prepared in 0.500 cm path-length cuvettes. Their absorbances are listed below.
Concentration (mM) | Absorbance (0.500 cm cuvette)
0.00 | 0.000
0.20 | 0.131
0.40 | 0.260
0.60 | 0.395
0.80 | 0.525
A fabric extract expected to contain the same dye is too concentrated to be placed in the short-path cuvettes, so its absorbance is measured in a 1.00 cm cuvette, giving a value of 0.774.
(a) Determine the molar absorptivity constant for the dye from the calibration data obtained with the 0.500 cm cuvettes.
(b) Using the value from part (a), calculate the concentration of the dye in the fabric extract measured in the 1.00 cm cuvette.
(c) Evaluate whether the concentration calculated in part (b) falls within the linear range established by the standards. If it does not, propose a specific dilution factor that would bring the sample into that range, and predict the absorbance you would expect after performing the dilution.
(d) Discuss one systematic error that could arise from switching between cuvettes of different path lengths and describe a procedural step that would minimize this error in future measurements.