A student prepares a calibration curve from a standard solution that is believed
ID: 479570 • Letter: A
Question
A student prepares a calibration curve from a standard solution that is believed to be composed of a single dye. However, the student does not realize that the color of the standard solution is actually composed of two different species of food dye, both of which absorb at the wavelength chosen for the curve. If a student uses this calibration curve to analyze a solution containing only one of the two dye species, what will happen to the student's calculated result for the unknown concentration?
a) Reported concentration wil be higher than actual
b) Reported concentration will be lower than actual
c) Reported concentration will be unaffected because it was prepared in the same way as the standards
d) No concentration value will be able to be determined because the instrument cannot read a different species than what the calibration curve was created from.
Explanation / Answer
b) Reported concentration will be lower than actual.
During preparation of caliberation curve, the absorbance is due to two components. Thus for a given concentration of standard solution, the reported absorbance is higher than the value corresponding to only one component. Hence, when the absorbance of an unknown sample is determined, the reported absorbance of unknown will be compared to higher absorbance of standard solution. Hence, the reported concentration will be lower than actual.
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