Green 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.

Some web references 12 Principles of Green Chemistry www.epa.gov/sciencematters/june2011/principles.htm Percent Yield Reference http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/percentt utorial.htm

12 Principle s of Green Chemistry What is Green Chemistry? Textbook p. 771- 775

18.9 Describe the basic goals of green chemistry. 18.61 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.

© 2012 Pearson Education, Inc. Green Chemistry We have become increasingly aware over the past 30 to 40 years that modern processes are not always compatible with maintaining a sustainable environment. Promoting chemical processes that are environmentally friendly is part of the good stewardship chemists should exhibit. © 2012 Pearson Education, Inc.

Green Chemistry Principles Prevention: It is better to prevent waste than to clean it up after it has been created. © 2012 Pearson Education, Inc.

Green Chemistry Principles Atom Economy: Methods to make chemical compounds should be designed to maximize the incorporation of all starting atoms into the final product. © 2012 Pearson Education, Inc.

Green Chemistry Principles Less Hazardous Chemical Syntheses: Wherever practical, synthetic methods should be designed to use and generate substances that possess little or no toxicity to human health and the environment. Design of Safer Chemicals: Chemical products should be designed to minimize toxicity and yet maintain their desired function. © 2012 Pearson Education, Inc.

Green Chemistry Principles Safer Solvents and Auxiliaries: The use of auxiliary substances should be eliminated wherever possible and, if used, should be as nontoxic as possible. Design for Energy Efficiency: Energy requirements should be recognized for their environmental and economic impacts and should be minimized (e.g., carry out reactions at room temperature and pressure). © 2012 Pearson Education, Inc.

Green Chemistry Principles Use of Renewable Feedstocks: A raw material should be renewable whenever technically and economically practical. Reduction of Derivatives: Unnecessary derivatization should be minimized or avoided if possible to save reagents and waste. Catalysis: Catalytic reagents improve yields within a given time and with less energy and are, therefore, preferred. © 2012 Pearson Education, Inc.

Green Chemistry Principles Design for Degradation: Chemical products should be designed so that at the end of their function they break down into innocuous products and do not persist in the environment. Real-Time Analysis for Pollution Prevention: Analytical methods should be developed to allow for real-time monitoring and control prior to the formation of hazardous substances. © 2012 Pearson Education, Inc.

Green Chemistry Principles Inherently Safer Chemistry for Accident Prevention: Reagents and solvents used in a chemical process should be chosen to minimize the potential for chemical accidents. © 2012 Pearson Education, Inc.

A 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 above Answer: D

Using 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 above Answer: B

Use 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 above Answer: D

18.9 Describe the basic goals of green chemistry. 18.61 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.

18.9 The 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.

18.61 A. 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.

Green Chemistry Analysis of a Mixture Mixture of bicarbonate/carbonate What 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!

Some experimental tips Some experimental tips! Why do you have to reheat the bicarbonate sample? How will that affect the results?

What needs to be included in the data table? Sodium bicarbonate Mass in grams Crucible cover sample Crucible and cover Bicarbonate sample Heat #1 Heat #2 Mass of H2O and CO2

Calculations- Analyze the Results Percent of the bicarbonate in the mixture Percent recovery Atom recovery Theoretical mass of product formed Na2CO3 Percent Yield Atom Recovery

Please 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)