Question

After you finish collecting your absorbance readings on the spectrophotometer, you notice a dark smudge on your cuvette you used to blank while doing a Beer's Law experiment. How would you expect this to have affected your absorbance readings on samples you ran after the blank?

a) It would increase the absorbance readings
b) It would decrease the absorbance readings
c) It would have no effect on the absorbance readings
d) It would make the readings inconsistent and unpredictable

Answer 1

A dark smudge on the blank cuvette would likely result in an increase in absorbance readings for subsequent samples measured in a Beer's Law experiment due to lowered transmittance and a falsely high baseline set by the spectrophotometer.

Step-by-step explanation:

If you discover a dark smudge on your cuvette that was used to blank the spectrophotometer during a Beer's Law experiment, it would likely lead to an increase in absorbance readings for the samples measured afterward. The smudge acts as an extra absorber of light, thus decreasing the transmittance of light through the cuvette. When the spectrophotometer is blanked with the smudged cuvette, it sets the baseline absorbance too high, causing all subsequent samples to have higher absorbance values than they should. This is because the spectrophotometer assumes that the smudge is part of the blank, and therefore, any additional absorbance from the actual samples is added to the already increased baseline.