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IN NO EVENT WILL THERMO ELECTRON CORPORATION BE LIABLE TO YOU OR ANY OTHER PARTY FOR DIRECT, INDIRECT, GENERAL, SPECIAL, INCIDENTAL, CONSEQUENTIAL, EXEMPLARY OR OTHER DAMAGES ARISING FROM THE USE OF OR INABILITY TO USE THE PRODUCT OR FROM ANY BREACH OF ANY WARRANTY, EVEN IF THERMO ELECTRON CORPORATION HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. (Some states do not allow the exclusion or limitation of incidental or consequential damages, so that above exclusion or limitation may not apply to you.) In no event shall the total liability of Thermo Electron Corporation exceed the amount you paid for the right to use this product. Because it is impossible for Thermo Electron Corporation to know the purposes for which you acquired this product or the uses to which you will put this product, you assume full responsibility for the selection of the product and for its use and the results of that use. ACKNOWLEDGEMENT Thermo Electron Corporation wishes to thank Professors Robert Smith and Michael Walczak of the Chemistry Department at St. John Fisher College in Rochester, New York, for rewriting this manual. We also extend our thanks to Linda Mocejunas and Beth Reabold at St. John Fisher College for their help in typing and formatting the experiments, and to the chemistry students of St. John Fisher College and those high school students from the Rochester, New York, area who tested these experiments and provided constructive feedback. Thermo Electron Corporation INTRODUCTION The experiments in this manual have been selected to provide high school and/or first-year college students with a variety of experiences using visible spectroscopy. Experiments 1-4 are basic experiments. Experiments 1 and 7 each involve building a spectrophotometer and then investigating how the instrument operates. Experiments 2-4 provide an introduction to spectroscopy: absorption spectra are recorded and the relationship between absorbance and concentration (shown by Beer's Law) is investigated. Experiments 5, 6, and 8-10 illustrate how visible spectroscopy can be employed to solve problems of chemical interest. Experiments 1-7 can be performed individually or in groups, and the experiments are designed so that all of the experimental data needed to answer the questions posed in the experiments can be collected in approximately one hour of lab time. Furthermore, all of the reagents needed in Experiments 2-5 can be purchased at a grocery store, and most of the reagents for Experiment 6 can be found at a pet store. Therefore, Experiments 1-7 are well-suited for high school students. Experiments 8-10 are intended to be performed individually, require approximately three hours each to complete, and are not easily broken into parts which could be done simultaneously. While these experiments are intended for college students, they could also be performed by high school students having a sufficiently long lab period. Each experiment in the lab manual has been written so that it can stand alone. No experiment makes reference to material in any other experiment in the manual. Any of the experiments may be copied for distribution to your students. The same format is used in each experiment. The “Introduction” states what is to be investigated and provides the background needed for that experiment. The “Experimental Procedure” section has detailed directions for performing the experiment; included in this section are safety warnings and directions for disposal of wastes. The “Calculations” section states specifically the quantities to be calculated and the questions to be answered. Pages for recording the data, showing calculations, and writing the answers to the questions are included in the “Report Form” section. The final section, “Notes to Instructor,” provides information about the amounts of chemicals and materials needed per person (or per group), directions for solution preparations, comments about expected experimental results, and answers to questions. In addition, some “Notes to Instructor” sections have additional information about safety matters and waste disposal. Whenever possible, the experiment uses only small quantities of reagents. Please read all warnings on the labels on the reagent bottles. The applicable Material Safety Data Sheet (MSDS) can be consulted for additional information, including medical response, about a specific chemical. Always have your students wear safety goggles, or other appropriate eye protection, when they are working in the laboratory. TABLE OF CONTENTS PAGE GENERAL OPERATING INSTRUCTIONS i. SPECTRONIC 20 SPECTROPHOTOMETER ............................... i-1 ii. SPECTRONIC 20D SPECTROPHOTOMETER .............................ii-1 iii. SPECTRONIC 20+ SPECTROPHOTOMETER ............................. iii-1 iv. SPECTRONIC 20D+ SPECTROPHOTOMETER ............................ iv-1 v. SPECTRONIC Educator SPECTROPHOTOMETER ......................... v-1 vi. GENESYS 20 SPECTROPHOTOMETER ................................. vi-1 EXPERIMENTS 1. Compact Disc (CD) Spectrophotometer .................................... 1-1 2. Absorption Spectrum................................................... 2-1 3. Determination of Concentration Using Beer's Law............................ 3-1 4. Importance of Wavelength Selected in the Beer's Law Experiment............... 4-1 5. Red Cabbage pH Indicator............................................... 5-1 6. Spectrophotometric Determination of Nitrate Ion Concentration ................. 6-1 7. Comparing the Performance of Two Spectrophotometers ....................... 7-1 8. Formula Determination by Continuous Variations ............................ 8-1 9. Determination of the Solubility Product of Copper (II) Iodate ................... 9-1 10.A Kinetics Experiment: Fading of Phenolphthalein.......................... 10-1 GENERAL OPERATING INSTRUCTIONS SPECTRONIC® 20 SPECTROPHOTOMETER GENERAL 1. Turn on the SPECTRONIC 20 by turning the power switch clockwise. Allow the spectrophotometer to warm up for at least fifteen minutes to stabilize the source and detector. 2. Set the desired wavelength with the wavelength control. 3. Adjust the meter to 0%T with the zero control knob. 4. Fill a clean cell with water (or another blank solution) and wipe the cell with a tissue to remove liquid droplets, dust and finger prints. Place the cell in the sample compartment and align the guide mark on the cell with the guide mark at the front of the sample compartment. Press the cell firmly into the sample compartment and close the lid. Adjust the meter to 100%T with the transmittance/absorbance control knob. Remove the cell from the sample compartment and empty the water. 5. When all measurements are completed, turn off the spectrophotometer by turning the power switch counterclockwise until it clicks. MAKING ONE OR MORE MEASUREMENTS AT THE SAME WAVELENGTH 1. Follow steps 1 through 4 above (“General”). 2. Rinse the cell twice with small volumes of the solution to be measured and fill it with the solution. Wipe the cell with a tissue and insert the cell into the sample compartment. Align the guide marks and close the lid. Read the appropriate value (%T or A) from the meter. 3. Remove the cell from the sample compartment and repeat step 2 for any remaining sample solutions. i-1 GENERAL OPERATING