The objectives of this experiment are a) to learn how to prepare standard solutions from a stock solution and b) to use these standard solutions to obtain a calibration curve for use in determining the concentration of an unknown solution.
In this experiment, you will prepare several ferroin solutions of precisely known concentrations (standard solutions). You will use a digital pipettor to deliver a small volume of the stock solution to a 10 mL volumetric flask and then add DI water to dilute the stock solution to the calibration mark etched on the neck of the flask. By using different volumes of the stock ferroin solution and diluting each to the same final volume, you will prepare several standard solutions of various concentrations.
Spectral analysis, specifically absorbance spectroscopy, will be used to evaluate the amount of light each of the ferroin solutions absorbs. You will use a calibration curve, which relates the absorbance of standard solutions to their known concentrations, along with the absorbance of a ferroin solution you prepare, to determine the concentration of ferroin in your solution.
The technique of performing dilutions of stock solutions to prepare standard solutions and the ability to use a calibration curve to determine the concentration of an unknown solution are common skills required for chemical analyses and both will be used in future Chem 152 labs, as well as in Chem 162.