Pre-Assignments

1. What is a calibration curve or calibration plot?
2. According to the Beer-Lambert law absorbance is proportional to concentration at each wavelength. In principle, one could choose any wavelength for quantitative estimations of concentration. However, we generally select the wavelength of maximum absorbance for a given sample and use it in our absorbance measurements. Especially, one should avoid the steep portions of the spectrum. Why?
3. Which concentration range - a dilute or a concentrated one - is chosen for accurate determinations of unknown concentrations?
4. One substance has ε 100 times more the other one. In which substance can one detect very small amounts of material?

Post-Assignments

1. Why the accuracy of calibration curve is of absolute importance?
2. What are steps should be taken to ensure the accuracy of calibration curve?
3. Draw two calibration plots for two peak positions of K ₂ Cr ₂ O ₇. Which linear fit is better? Find out the correlation coefficients of the two straight lines.
4. What is difference between the values of unknown concentration determined from two calibration plots of K ₂ Cr ₂ O ₇? Justify your answer.