Presentation on theme: "Green Chemistry Section 18.5"— Presentation transcript:
1Green Chemistry Section 18.5 Green Chemistry Program was initiated by the Environmental Protection Agency in the 1990s with the goal of applying chemical principles to prevent pollution. The program calls for the design of chemical products and processes that will reduce the use and generation of hazardous substances.The purpose of our next lab is to design an experiment for determining the percent composition of a solid by applying the principles of green chemistry.
2Some web references 12 Principles of Green Chemistry Percent Yield Referenceutorial.htm
312 Principle s of Green Chemistry What is Green Chemistry?Textbook p
418.9 Describe the basic goals of green chemistry. Which choice is greener in a chemical process? EXPLAIN. (a) benzene as a solvent or water as a solvent. (b) the reaction temperature is 500 K , or 1000 K. (c) NaCl as a by-product or chloroform (CHCl3) as a by- product.
13A catalyst speeds up a chemical reaction and this reduces energy costs of production. A catalyst may permit a reaction to run at a lower temperature and reduces energy costs of production.A new catalyst may replace a more expensive catalyst and permit use of less expensive reagents by changing the pathway of the reaction.All of the aboveAnswer: D
14Using carbon dioxide in reactions can reduce significantly the amount of carbon dioxide in the atmosphere.Supercritical carbon dioxide is a solvent that can replace toxic solvents in some situations.A product of some reactions of carbon dioxide is carbon monoxide and this is desirable.None of the aboveAnswer: B
15Use room temperature and room pressure. Use water as a solvent if possible.Use oxygen as the oxidizing agent instead of hydrogen peroxide if possible.All of the aboveAnswer: D
1618.9 Describe the basic goals of green chemistry. Which choice is greener in a chemical process? EXPLAIN. (a) benzene as a solvent or water as a solvent. (b) the reaction temperature is 500 K , or 1000 K. (c) NaCl as a by-product or chloroform (CHCl3) as a by- product.
1718.9The guiding principle of green chemistry is that “ an ounce of prevention is worth a pound of cure”. Processes should be designed to minimize or eliminate solvents and waste, generate nontoxic waste, be energy efficient , employ renewable starting materials, and take advantage of catalysts that enable the use of safe and common reagents.
1818.61A. Water as a solvent is much “greener” than benzene, which is a known carcinogen. Water fits criteria (5) safer solvent, (7) renewable feedstock and (12) inherently safer for accident prevention.B. Reaction temperature of 500 K rather than 100 K is “greener, according to criteria (t6) design for energy efficiency and (12) inherently safer chemistry for accident prevention. Also, low temperature is less likely to produce undesirable by products that have to be separated and treated as waste, which is criterion (1)C. NaCl as a byproduct rather than chloroform CHCl3 is “greener”, according to criteria (1) prevention, (3) less hazardous chemical systems, and (12) inherently safeter (CHCl3 is flammable while NaCl is not.
19Green Chemistry Analysis of a Mixture Mixture of bicarbonate/carbonateWhat happens when you heat a bicarbonate?What happens when you heat a carbonate? Above 800oC?What are the products of the reaction?1MHCO3(s) M2CO3(s) + H2O(g) + CO2(g)Carbonates do NOT undergo decomposition below 800oC!
20Some experimental tips Some experimental tips! Why do you have to reheat the bicarbonate sample? How will that affect the results?
21What needs to be included in the data table? Sodium bicarbonateMass in gramsCrucible cover sampleCrucible and coverBicarbonate sampleHeat #1Heat #2Mass of H2O and CO2
22Calculations- Analyze the Results Percent of the bicarbonate in the mixturePercent recoveryAtom recoveryTheoretical mass of product formed Na2CO3Percent YieldAtom Recovery
23Please Include in Your Lab Report Error Analysis and Conclusion Error Analysis: Predictions are made about your error in measurement. How did your error in measurement affect your calculated value?Conclusion: Include a one-to two- sentence summary of results. This is a separate section of the report. (Sum of the analysis with an explanation)