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Newly available from Brooks/Cole is Stanton/Zhu/Atwood’s Experiments for General Chemistry, Featuring MeasureNet. This lab manual includes 28 concept/ technique-oriented and self-directed, general chemistry laboratory experiments using the MeasureNet system. Visit the book website to learn more and to order a sample copy. |
The following lab experiments, featuring the MeasureNet System, are available for inclusion in your custom lab manual, either on their own, or in combination with lab modules from CER. Labs can be viewed in their entirety and ordered at www.TextChoice.com.
Tools for Lab Measurement
This is an introduction to the use of MeasureNet in the lab. The temperature probe is calibrated, a data set (temperature vs. time) is collected and a graph is printed. The measurement of mass and volume is also examined in some detail. Group results for the volume of water measured out using various types of glassware are combined into histograms to reveal the differences in precision and accuracy.
Introduction to Spectroscopy
This is an introduction to the use of the MeasureNet networked diode array spectrometer. Both emission and absorption spectra are measured. The group measures the absorption spectrum of a substantial number of solutions (three different solutes, numerous concentrations) so that the results can be used to produce Beer's Law plots of the combined spectra. As a final step, the concentration of an unknown solution is determined by means of these plots.
Reaction Stoichiometry and Moles
The students on one MeasureNet network prepare and measure the absorption spectra of a large number of solutions containing Fe2+ ions and an organic ligand. All solutions have the same concentration of the ligand, but the iron ion concentration varies from much less than to much more than the ligand concentration. From a graph of the absorbance at the peak maximum as a function of iron ion concentration the stoichiometric ratio of ligand to iron ion in the complex is determined.
Reaction Stoichiometry
The temperature rise caused by an exothermic oxidation-reduction reaction is measured. The experiment is repeated a number of times keeping two things constant: the total volume of the reaction mixture, and the sum of the numbers of moles of the two reactants. Under these conditions, the experiment in which stoichiometric amounts of the reactants are combined results in the maximum temperature rise, and this provides the means for determining the stoichiometry of the reaction.
Enthalpy of Reaction - Hess's Law
The enthalpy change is experimentally determined for each step in two alternative pathways from reactants to products. The overall change in each of the two pathways is then found and the two values are compared to test the validity of Hess's Law.
Line Spectra of Elements
The MeasureNet networked diode array spectrometer is used in emission mode to measure a variety of emission spectra. The first is the spectrum of the H atom from a gas discharge tube. The line positions are related to the electronic structure of the H atom. The remaining spectra are of flames into which various salt solutions are introduced. The students as a group measure and share the emission spectra of a series of known salt solutions. Each pair of students then measures the flame emission of each of several unknown solutions. The unknowns contain one, two, or three of the salts present in the known solutions.
Behavior of Gases
Using a plastic syringe attached to the pressure probe, the PV behavior of air at room temperature is investigated and found to confirm Boyle's Law. The temperature is varied for a gas sample in a container of essentially constant volume and the pressure is measured. Amontons' Law is confirmed, and a (crude) value of absolute zero is found by means of extrapolation.
Vapor Pressure and Heat of Vaporization
The pressure of air in a closed container is measured at a series of temperatures. A volatile liquid is then injected, and the total pressure is again measured over the temperature range. The contribution due to air is subtracted out, and the remaining pressure values, the vapor pressure of the liquid at various temperatures, are analyzed to determine the heat of vaporization of the liquid.
Freezing Point: A Colligative Property of Solutions
Each pair of students on a MeasureNet network measures cooling curves for several solutions of cyclohexane with napthalene, biphenyl, or diphenylamine as solute. Freezing points are determined from the cooling curves and are combined in one graph of freezing point vs. molality. From this graph the students discover the factors affecting, or not affecting, the freezing point. Each pair of students then prepares a solution with an unknown solute and determines its freezing point. This is used to determine the molecular weight of the unknown solute.
Spectrophotometric Determination of an Equilibrium Constant
A series of buffer solutions is first prepared to cover the pH range indicated by the instructor. These buffer solutions are then used to prepare a series of solutions containing a fixed concentration of an acid-base indicator. The pH range chosen results in solutions containing the indicator all in acid form, all in base form, and at a number of intermediate pH values in which both forms are present. The absorption spectrum is measured for each of these solutions and the absorbance at a chosen wavelength is determined for each. These values are analyzed to yield the pK of the indicator.
Acidic and Basic Salts
The pH is measured for each of a series of dilute solutions of acids, bases, and salts, and these values are compared with expected behavior based on the chemical nature of the species. A buffer solution is prepared and its resistance to changes in pH is investigated.
Electrochemistry: Voltaic Cells
A series of simple half-cells is used to construct voltaic cells. The MeasureNet station voltage mode is used to determine the cell potential for each cell. One half-cell is chosen as a reference, and the cell potentials are used to construct a simple table of half-cell reduction potentials. The effect on cell potential of varying ion concentrations in a half-cell is also investigated.
The Cola Project - Analysis of Phosphate in Cola
This is a multi-week project in which groups of four students determine the amount of phosphate in cola by two different methods: acid-base titration and a spectrophotometric determination by means of a complex ion formed.
The Cobalt Project - Synthesis and Identification of Coordination Compounds
This is a multi-week project in which a series of cobalt complexes are synthesized and examined, particularly by means of visible spectroscopy.
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