An analyte has a molar absorptivity of at 510 nm and at 620 nm
CHEMISTRY · Single correct · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
An analyte has a molar absorptivity of 1.5×104Lmol−1cm−1 at 510 nm and 4.0×103Lmol−1cm−1 at 620 nm. A 1.00 cm cuvette containing a 2.0×10−5M solution of the analyte is analyzed at both wavelengths.
Which statement about the relative sensitivity of the two measurements is correct?
(a) Both wavelengths provide identical sensitivity because absorbance is directly proportional to concentration at either wavelength.
(b) The measurement at 620 nm is about four times more sensitive because the smaller molar absorptivity produces a lower instrumental noise.
(c) The measurement at 510 nm is about four times more sensitive because its absorbance is roughly 0.30 compared with 0.08 at 620 nm.
(d) The measurement at 620 nm is preferred because its absorbance is about 0.8, which falls in the optimal 0.2–1.0 range, whereas the 510 nm absorbance is nearly 3 and therefore outside the linear range.