During an absorbance experiment a student notes that the calibration curve is linear…
CHEMISTRY · Single correct · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
During an absorbance experiment a student notes that the calibration curve is linear up to about 1.0 absorbance unit, after which additional data points curve downward from the extrapolated line. Which statement best explains this behavior and predicts what will happen if the path length of the cuvette is doubled while everything else remains the same?
(a) Detector dark current adds a constant offset to all readings; doubling the path length eliminates the curvature because absorbances double.
(b) The detector becomes saturated by intense light at low absorbance; doubling the path length lowers the light intensity and allows the detector to respond linearly, so curvature disappears.
(c) Stray light reaching the detector lowers apparent absorbance at high A; doubling the path length shifts the onset of curvature to lower concentrations.
(d) Chemical equilibrium shifts at higher concentrations, reducing true absorbance; doubling the path length restores linearity because path length is now the controlling variable.