Slide 1 / 25 Slide 2 / 25 New Jersey Center for Teaching and Learning Applying Green Chemistry to Purification Progressive Science Initiative The goals of this lab are to: This material is made freely available at www.njctl.org and is intended for the non-commercial use of · Design a procedure to separate two students and teachers. These materials may not be used for any commercial purpose without the written substances using the principles of green permission of the owners. NJCTL maintains its website for the convenience of teachers who wish to chemistry. make their work available to other teachers, participate in a virtual professional learning · Assess the quality of a lab report community, and/or provide access to course materials to parents, students and others. submitted for peer review before being published. Click to go to website: www.njctl.org Slide 3 / 25 Slide 4 / 25 Background 1 List as many physical properties of matter you can think of Students type their answers here that can be used to distinguish two substances from one another. What chemists do is design chemicals and chemical processes. These practices involve a few main principles. One of these is that pure substances have unique properties that can be used to distinguish them from one another. A second principle is that chemists consider the benefits and risks of different options when deciding which is the best chemical process. These two principles form the focus of this experiment. Slide 5 / 25 Slide 6 / 25 Principles of Green Chemistry Principles of Green Chemistry The 12 priniciples of green chemistry are also considered in Principle 2 is called the Atom Economy principle. the purification of a mixture. The less is left over, the better. In the most ideal case, all of the starting materials are converted into 1. Create no waste. 2. Nothing should be left over. the desired product and there is nothing left over. 3. No toxicity. In order to compare processes in terms of how 4. Green products have to work as well as nongreen much is left over, atom economy is calculated. products. 5. Get rid of all non essential additives. 6. Reduce energy usage. 7. Use renewable materials. 8. Get rid of as many steps as possible. 9. Make use of a reusable method to speed up a reaction. 10. Use materials that break down in the environment (biodegradable). 11. Check everything you do against the other principles. 12. Safety first.
Slide 7 / 25 Slide 8 / 25 Principles of Green Chemistry 2 If the atom economy of a reaction is less than 100% what Students type their answers here does that say about the reaction? Atom economy = mass of desired product (D) x 100 % mass of total product (T) When D/T = 100% then there is nothing left over because there is only one product, the desired one. Slide 9 / 25 Slide 10 / 25 3 The following two reactions are possible methods for 4 Which method creates the least amount of waste? Which Students type their answers here refining copper in the final step of a smelting process, i.e., has the higher atom economy? getting pure copper (Cu) from copper ores found in rocks. Calculate the theoretical atom economy for each reaction. A Reaction 1 B Reaction 2 2CuO (s) + C (s) 2Cu (s) + CO 2 (g) CuO (s) + CO (g) Cu (s) + CO 2 (g) Slide 11 / 25 Slide 12 / 25 5 Why is a calculation of atom economy helpful in Students type their answers here 6 What is another possible consideration from principles of Students type their answers here comparing two chemical reactions to determine which one green chemistry that could tell you more about comparing is greener? In other words, what does atom economy tell you about "greenness"? the "greenness" of these two reactions?
Slide 13 / 25 Slide 14 / 25 7 Peer review is a critical component of how scientists 8 Why is peer review an important part of a process of communicate what they have learned and contribute to Students type their answers here chemists considering benefits and risks? Why might peer Students type their answers here new knowlege. What is peer review? Why do you think review be important in chemists reporting results of a that scientists believe it is important for published work to chemical process? be peer reviewed prior to publication? Slide 15 / 25 Slide 16 / 25 Materials: A mixture of sodium bicarbonate and sodium carbonate, scoopula, Bunsen burner (hot plate), ring stand, wire gauze, crucible and cover, balance, weighing paper, electronic scale, and tongs. Guided Lab - Procedure and Examples Setup: Each group of up to 3 students is given access to or is given the · materials listed above. Slide 17 / 25 Slide 18 / 25 Procedure Roles Lab teams should consist of up to 3 students. The students should take turns and rotate through the roles listed below. Students will determine their procedure as to how many times and how · As a team, the students will outline their procedure. long to heat the mixture. 1. One person is responsible for massing the crucible and cover, and the crucible and cover and sample before the experiment begins and after each heating. 2. One person records the observations. 3. One person is responsible for collecting the mass data and leading the completion of the calculations.
Slide 19 / 25 Slide 20 / 25 Safety Warning: Special Considerations Always place the lid askew on the top of the crucible while heating. · Use all due caution with the Bunsen burner or hot plate. · Do not heat covered crucibles. Always place the lid askew on top of · Hot things (like evaporating dishes and metal rings) look like cold things; do · the crucible while heating. Completely covering the crucible is not touch anything with bare hands. dangerous because gases can build up inside while heating and hot Students must pull back their hair to avoid a fire hazard. · lids can fly off. Instructors should also familiarize students with the location of laboratory · safety equipment. Students should know where to find running water, an Allow the crucible and cover dish and sample to cool for 5 minutes and · eyewash and shower, an emergency blanket and the fire extinguisher before then mass and record the mass to the nearest 0.01 g or better. beginning the lab. Consider as you complete the lab possible sources of error. · Tell the instructor of any accidents immediately. · Keep food and drinks out of the laboratory work area. · Slide 21 / 25 Slide 22 / 25 Data Collection · Collect mass data on your crucible cover and sample after each heating. Mass determinations should be made on items that have completely cooled. Analysis and Application · Make observations before, during and after Questions heating your sample. Slide 23 / 25 Slide 24 / 25 10 Analysis of a sample of Chromium (III) nitrate hydrate 9 A 4.218 g sample of a mixture of sodium bicarbonate and Students type their answers here Students type their answers here finds that it is 40.50% water by mass. What is the sodium carbonate is heated and has a final mass of 2.924 g. chemical formula and name of this hydrate? What is the relative mass of each of the substances in the mixture?
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