Page 20 - Demo

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Flinn Lab Activities and Demonstrations
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Guided-Inquiry Experiments for General Chemistry, continued
Green Chemistry Analysis of A Mixture—
Laboratory Kit
By: The Flinn Staff
Many stoichiometry experiments use hazardous chemicals, generate toxic byproducts, and waste excess chemicals. In this lab activity, students design and carry out a green chemistry experiment that can quantitatively measure the weight percent of one compound in a mixture of two compounds.
The investigation begins with an introductory activity to verify the decomposition reaction of a solid bicarbonate, either potassium or sodium bicarbonate. Students review the principles of green chemistry and evaluate a stoichiometry lab procedure in terms of prevention, atom economy, and use and production of nontoxic materials.
Once the introductory activity is completed, students design and carry out an experiment to quantitatively measure the weight percent of solid mixtures containing either sodium carbonate and sodium bicarbonate or potassium carbonate and potassium bicarbonate. Students assess their procedures in terms of the green chemistry principles.
Complete for 24 students working in pairs.
Kinetics of Crystal Violet Fading—Laboratory Kit
By: The Flinn Staff
One of the most important considerations in a “green chemistry” analysis is how fast a chemical degrades. In this advanced inquiry lab, students use spectroscopy and graphical analysis to determine the rate law for the color-fading reaction of crystal violet with sodium hydroxide.
Students begin by constructing a calibration curve of absorbance versus concentration for crystal violet. A series of known or standard solutions is prepared from a stock solution of crystal violet and the absorbance of each solution is measured at an optimum wavelength. A Beer’s law plot of absorbance as a function of concentration may be used to calculate the concentration of an “unknown” solution of the dye in a rate law experiment.
This procedure provides a model for the guided-inquiry portion of the lab, during which students design experiments to determine the order of reaction with respect to both crystal violet and sodium hydroxide. Two dyes with similar structures, malachite green and phenolphthalein, are provided for optional extension studies.
Complete for 24 students working in pairs.
Percent Copper in Brass—Laboratory Kit
By: The Flinn Staff
The purpose of this guided-inquiry lab is to design a procedure to analyze the amount of copper in brass using visible spectroscopy. The lab begins with an introductory activity, in which students measure the absorbance of various metal ion solutions at regular wavelength intervals from 400 nm to 700 nm and investigate the influence of the anion on the absorption spectra. Students identify the correlation among wavelength, absorbance, and concentration for each of three possible ions that may be obtained from brass: copper, zinc, and iron.
Once the introductory activity is completed, students design and carry out an experiment to construct a calibration curve and determine the concentration of copper ions in a solution prepared by dissolving brass in nitric acid. Students must investigate the concentration range over which Beer's law is valid and identify the optimum wavelength for analysis. The mass percent of copper in brass is determined from the results of the analysis.
Complete for 24 students working in pairs.
Green Chemistry Analysis of A Mixture—Laboratory Kit AP7974
Catalog No.
Description
Price/Each
AP7974
Green Chemistry Analysis of A Mixture—Laboratory Kit
$28.65
Catalog No.
Description
Price/Each
AP7975
Kinetics of Crystal Violet Fading—Laboratory Kit
$39.45
Kinetics of Crystal Violet Fading—Laboratory Kit AP7975
Percent Copper in Brass—Laboratory Kit AP7976
Catalog No.
Description
Price/Each
AP7976
Percent Copper in Brass—Laboratory Kit
$59.30
GUIDED-INQUIRY EXPERIMENTS FOR GENERAL CHEMISTRY continued on next page.