|The copper solution from the brass and nitric acid reaction.|
|I added the nitric acid in the fume hood.|
Eventually, once we all got our fill of watching copper oxidize, my kids went about the task of preparing standard solutions for a calibration curve that will allow them to determine just how much copper was in their brass sample. The class worked cooperatively to prepare four solutions with concentrations ranging from 0.05 to 0.40 M of copper(II) nitrate. Beer's law tells us that there is a linear relationship between the absorbance of a solution and the concentration. No, there were no alcoholic beverages served in this experiment! The quantity of the copper in the reaction mixture, and thus the brass shot sample, is calculated from the equation for the line in the calibration curve. The data for this lab was so wonderful. We got r-squared values of 0.99 and even a 1!
|The reaction between copper and nitric acid is fun to watch.|
|One of the calibration curves from the lab, very nice.|