Roses are Red, Solutions are Violet at PHHS

Students stand and hold up their hands.Patrick Henry AP chemistry students completed a laboratory exercise using crystal violet dye to measure rate of change. This key lab in the kinetics unit measures the change in light transmission using a strongly basic solution and crystal violet. The dye fades from a strong violet color to colorless in the basic solution.

Students measured the light transmission using Vernier colorimeters set to a wavelength of 565nm. They then graphed the rate of change in concentration of crystal violet versus time to determine the order of the reaction and the rate law. This lab requires a careful approach as crystal violet stains everything in comes in contact with, the strongly basic solution of sodium hydroxide is corrosive, and the colorimeter is sensitive to smudges on the cuvette as well as interference of other light wavelengths. The results left the students tickled pink……I mean violet!

Contact Person: 
Tina Osborne