Transcript Green Chemistry - christine

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.
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.
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Green Chemistry Principles
1.
Prevention: It is better to prevent
waste than to clean it up after it
has been created.
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Green Chemistry Principles
2.
Atom Economy: Methods to make
chemical compounds should be
designed to maximize the
incorporation of all starting atoms
into the final product.
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Green Chemistry Principles
3.
4.
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.
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Green Chemistry Principles
5.
6.
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).
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Green Chemistry Principles
Use of Renewable Feedstocks: A raw material
should be renewable whenever technically
and economically practical.
8. Reduction of Derivatives: Unnecessary
derivatization should be minimized or
avoided
if possible to save reagents and waste.
9. Catalysis: Catalytic reagents improve yields
within a given time and with less energy and
are, therefore, preferred.
7.
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Green Chemistry Principles
10. 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.
11. 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.
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Green Chemistry Principles
12. Inherently
Safer Chemistry for
Accident Prevention: Reagents and
solvents used in
a chemical process should be chosen
to minimize the potential for chemical
accidents.
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A.
B.
C.
D.
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
A.
B.
C.
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
A.
B.
C.
D.
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
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?
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
Calculations- Analyze the Results
Percent of the bicarbonate in the
mixture
2. Percent recovery
3. Atom recovery
1.
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)