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Analysis of a Hazardous Spill |
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INTRODUCTION Background: Part of the role that chemistry plays in
our society is being able to determine what things are made of so that we can
take proper precautions if something should be dangerous. Part of the way that this is accomplished
is that since certain classes of chemicals have known reactions, this
information can be used to identify different materials. In this laboratory exercise you will be
provided with a scenario, a series of test procedures and an unknown chemical
to identify. Scenario: Your team works for a company that
identifies materials and makes recommendations to government officials as to
whether or not the material is hazardous.
Your company receives a call regarding what appears to be a white
powdery substance that has apparently been spilled either accidentally or
intentionally along the banks of the river that runs through your
community. Adjacent to the site is a
bridge that crosses the river. Several
manufacturing companies are located along the river or transport material
through town using the bridge that crosses the river. These companies include the following: |
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Ajax
Salt Company Beta
Agricultural Chemical Company Citywide
Distributors, Inc. Dewey
Brothers Industrial Supply Company Echo
Bay Sugar Manufacturing, Inc. Fox
Soap Company |
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Ajax makes and
sells table salt or sodium chloride; Beta makes corn starch; Citywide
Distributors is a major warehouser and shipper of sodium bicarbonate; Dewy
sells calcium carbonate which is used in some baking products; Echo Bay deals in sugar; and Fox sells
sodium phosphate, a material included in some types of detergent. The material could
have fallen off a truck passing over the bridge; or come from a barge that
uses the bridge for transport and was tied up temporarily under the
bridge. Each of the substances is a
white powder with certain physical and chemical properties. Objective: Your task is to use the procedures detailed
below to identify the material in your unknown sample. Your team will prepare a table of the
team's results and each team member will then write a report to the city
officials describing the incident, the test procedures, the results, the
conclusions. Included in the
conclusions are to be recommendations on what additional information would be
useful to make the study more thorough as well as any suggestions you might
have that would prevent such incidents in the future. |
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PROCEDURE For test requiring water you should also include a water
control. Test
1: Physical Description 1. Use a microscope
and microscope slides to make observations of each substance. 2. Draw
a picture of what you see for each substance and your unknown and record your
observations in your data table. Test
2: Solubility Test 1 . Label
7 test tubes or portion cups "A", "B", "C",
"D", "E", "F" and "Unknown #1". 2. Determine
the tare weight of a folded piece of paper. Weigh 0.2 g of each substance
onto the paper (a separate paper for each substance). Transfer the substance from the paper to a
13 mm by 100 mm test tube.. 3. Add
3 mL H20 in each portion
cup or test tube. 5. Swirl
the mixture for several minutes until you can establish whether or not the
material will dissolve. 6. Record
your observations in your data table. 7. Save
your solutions or suspensions for Test #3, the pH Test, Test #4 the Acid Test
and Test #7, the Conductivity Test. Test
3: pH Test 1. Place about 10-15
drops of each solution in one of several wells on your spot plate (be sure to
label or record and resuspend if the material is not soluble in the water). 2. Add two to three drops of pH
indicator solution each of the wells and record the color. 3. Compare
the color to that of a control (which should be???) and a color chart of
pH. 4. Record
your data in your data table. 5. Rinse and dry your
spot plate. Test
4: Acid Test 1. Place about 10-15
drops of each solution in one of several wells on your spot plate (be sure to
label or record and resuspend if the material is not soluble in the water). 2. Add 2 to 3 drops (drop by drop) of hydrochloric
acid in each well with the substance. 3. Record
your observations in your data table. 4. Rinse and dry your
spot plate. Test
5: Iodine Test 1. Place
a small amount of each substance in one of several wells on your spot plate. 2. Place
one drop of KI2 solution (Lugol's solution) on each substance in
the cup or test tube. 3. Record
your observations in your data table. 4. Be
sure to rinse the test tubes or cup plate before moving on to next test. Test
6: Benedict's Test 1. Place
a small amount of each substance in a test tube (one per substance). Add approximately 1.0 mL of water and swirl
gently to either mix or dissolve. 2. Add
ten (10) drops of the Benedict's Reagent to each test tube. You must use
to safety glasses to observe the results of this test. 3. Place
the test tubes in a boiling water bath for about 5 minutes. 4. Remove
tubes using test tube holder and allow tubes to cool. 5. Records
your observations in your data table. 6. Rinse
the tubes and return to the test tube rack. Test
7: Conductivity Test 1 . Place
about 10-15 drops of each solution in one of several wells on your spot plate
(be sure to label or record and resuspend if the material is not soluble in
the water). 2. Using
the conductivity meter, test the conductivity of each solution (and that of
water) 3. Record
your observations in your data table. |
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QUESTIONS 1. Using
resources in the classroom or on the Internet determine what is it exactly
that "pH" measures? 2. From
your results what do you think the Benedict's test determines. Examine the material in the bottom of the
tube where a color change took place.
What do you think that material is?
(The blue solution contains Cu2+). 3. What
does the iodine test detect? Can you
think of other substances that might be iodine positive? 4. What
does the acid test indicate as a positive reaction? What is the substance that is evolved? 5. Are
any of these materials, if dumped into our water supply actually
harmful. If so how? 6. What
is the distinction between a physical and a chemical property? Which tests test a physical property and
which test a chemical property? 7. Which
of these tests are these tests qualitative and which are quantitative? |
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