Do you expect the absorbance measured by the student in the video to be higher or lower than the actual absorbance of the solution? Why?
Answer
Since the sample solution was added to a cuvet that contained a small amount of water, the solution was diluted and its concentration decreased. According to Beer's law, absorbance varies directly with
concentration, so when the concentration of the sample decreased, the absorbance of the sample also decreased. The cuvet should have been rinsed with the sample solution before it was filled. In addition, the water on the outside of the cuvet could cause inaccurate measurements or damage the instrument. The water on the
outside should be removed with a lab tissue.
A student is measuring the absorbance of a solution of iodine in hexane. Suggest an appropriate reference sample.
Answer
A reference sample of pure hexane should be chosen. The analyte is iodine so using a hexane reference will compensate for absorption due to the solvent.
Do you expect the absorbance measured by the student in the video to be higher or lower than the actual absorbance of the solution? Why?