RAINY DAY ACTIVITY
9. Acid Rain
Rainy Day Activity
Student Instruction Sheet
Challenge
Use gas generators to produce the components of acid rain and determine which
type of gas causes the greatest change in pH when dissolved in water.
Equipment and Materials
• computer with USB port
• graduated cylinder, 100-mL
• PASPORT pH Sensor
• DataStudio software
• sodium bicarbonate (NaHCO3), 5.0 g
• sodium bisulfite (NaHSO3), 5.0 g
• Small Tripod Base & Rod
• sodium nitrite, (NaNO2), 5.0 g
• beaker (4), 100-mL
• test tube, medium (20 by 150 mm)
• beaker (3), 250-mL
• wash bottle and waste container
• beral-type pipet, thin stem (2.5 mm dia.) (3)
• water, distilled, 1.0 L
• beral-type pipet, wide stem (7.8 mm dia.) (3)
• protective gear
• beral-type pipet with 1.0 M HCl
• Student Instruction Sheet
• Buret Clamp
• Student Response Sheet
Safety Precautions
Remember, follow the directions for using the equipment.
Keep water away from electrical outlets, the computer,
keyboard, and the PASPORT equipment!
Wear safety glasses and follow standard laboratory
safety procedures.
Dispose of chemicals as directed by your instructor.
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9. Acid Rain
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Background
"Acid rain" is a broad term used to describe several
ways that acids fall out of the atmosphere. A more
precise term is acid deposition, which has two parts:
wet deposition and dry deposition.
Scientists discovered that sulfur dioxide (SO2) and
nitrogen dioxide (NO2) are the primary causes of acid
rain. Coal-burning power plants and automobile
exhaust are two sources of these gases. Acid rain occurs when these gases react
in the atmosphere with water, oxygen, and other chemicals to form various acidic
compounds. The result is a mild solution of sulfuric acid and nitric acid.
Acid rain is a global pollution issue. Prevailing winds blow the compounds that
cause acid rain across state and national borders, and sometimes over hundreds
of miles.
Acid rain is measured using a scale called "pH." The lower a substance's pH, the
more acidic it is. Pure water has a pH of 7.0. Normal rain is slightly acidic because
carbon dioxide dissolves into it, so it has a pH of between 5.5 and 6.0. (As a
reference, the hatching success of trout fish eggs is lowered when the pH of the
water falls below 5.5.)
Acid rain causes acidification of lakes and streams and contributes to damage of
trees at high elevations and many sensitive forest soils. In addition, acid rain
accelerates the decay of building materials (such as limestone and marble),
metals (such as bronze), automotive paint, and other coatings. Prior to falling to
the Earth, the components of acid rain contribute to visibility degradation and
harm public health.
Acid rain produces fluctuations in water systems causing aquatic life to
experience chemical "shock" effects. (For example, as the pH reaches 5.5
plankton, certain insects, and crustaceans begin to die.) Acid rain reduces crop
productivity and forest growth rates. Acid rain accelerates the rate at which
heavy metals are leached (dissolved) from soils, rocks, and sediments of
waterways.
Increasing
Acidity
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Neutral
Student Instruction Sheet PS-2809
Increasing
Alkalinity
RAINY DAY ACTIVITY
9. Acid Rain
Predict
Before beginning the eLab, complete the prediction and vocabulary portions of
the Student Response Sheet.
Explore
Computer Setup
1. Plug the PASPORT interface(s) into the computer’s USB port.
2. Plug the pH Sensor into
the PASPORT interface.
This will automatically
launch the PASPortal
window.
To computer
3. Choose the appropriate DataStudio configuration file entitled
09 Acid Rain CF.ds
and proceed with the following instructions.
Note: Configuration files automatically launch the appropriate
display(s), sampling rate(s), etc.
Equipment Setup
Setup the Test Tube and Sensor
1. Put 4.0 mL of water into a medium test tube.
2. Use a clamp to mount the test tube on a support rod.
3. Rinse the pH electrode with distilled water and then put it
into the test tube. (Make sure that the pH electrode is
connected to the pH Sensor.)
Create the Gas Generators
Instead of collecting gases from a coal-burning power plant
or from automobile exhaust, you will use chemical compounds
to produce the gases that form acid rain:
• Use sodium bicarbonate (sodium hydrogen carbonate), NaHCO3, with
hydrochloric acid, HCl, to produce carbon dioxide gas, CO2.
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9. Acid Rain
RAINY DAY ACTIVITY
• Use sodium bisulfite (sodium hydrogen sulfite), NaHSO3, with hydrochloric
acid to produce sodium dioxide gas, SO2.
• Use sodium nitrite, NaNO2, with hydrochloric acid to form nitrogen dioxide
gas, NO2.
1. Label three wide-stem Beral pipets with the formula of the chemical
compound they will contain:
• NaHCO3 (sodium bicarbonate)
• NaHSO3 (sodium bisulfite)
• NaNO2 (sodium nitrite)
2. Label three thin-stem Beral pipets with the formula of the gas they will
contain:
• CO2 (carbon dioxide)
• SO2 (sodium dioxide)
• NO2 (nitrogen dioxide)
3. Use a small beaker as a holder for the pipets.
• Your teacher will supply a beaker containing powdered NaHCO3 (sodium
bicarbonate).
4. Squeeze the bulb of the wide-stem pipet labeled NaHCO3 to push the air out
of the bulb.
5. Place the open end of the pipet into the powdered NaHCO3.
6. Release the bulb to draw some of
the powdered NaHCO3 into the
pipet.
7. Draw the powder into the pipet
until there is just enough powder
to fill the curved end of the bulb
of the pipet when you hold the
pipet with the bulb end down.
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9. Acid Rain
8. Repeat the previous step to fill the NaHSO3 (sodium bisulfite) and NaNO2
(sodium nitrite) wide-stem Beral pipets with the corresponding chemical
compounds. Store the filled pipets (bulb end down) in a small beaker.
9. Get a thin-stem Beral pipet with 1.0 M hydrochloric acid (HCl) from your
instructor.
Caution: Hydrochloric acid is a strong acid. Hold the pipet
gently, with the stem pointing up, so that HCl does not leak out.
10. Insert the narrow stem of the HCl pipet into the
larger opening of the wide-stem pipet with the
NaHSO3.
11. Gently squeeze the HCl pipet to add about 20 drops
of the acid solution to the powdered NaHSO3.
12. When finished, remove the HCl pipet. Gently swirl
the pipet that contains NaHSO3 and HCl.
13. Carbon dioxide gas, CO2, is generated in this pipet.
Place the pipet with the bulb end down in the small beaker to prevent spillage.
14. Repeat this same procedure a second time to add HCl to the pipet with the
powdered NaHSO3 (sodium bisulfite). Sulfur dioxide (SO2) is generated in
this pipet. Place this second pipet bulb end down in the small beaker to prevent
spillage.
15. Repeat this same procedure a third time to add HCl to the pipet with the
powdered NaNO2 (sodium nitrite). Nitrogen dioxide (NO2) is generated in this
pipet. Place this third pipet bulb end down in the small beaker to prevent
spillage.
Collect the Gas
1. Squeeze all of the air from the bulb of
the thin-stem pipet labeled "CO2".
2. Keep the bulb completely collapsed and
insert the long stem of the pipet down
into the gas-generator "NaHCO3"
pipet.
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9. Acid Rain
RAINY DAY ACTIVITY
• The tip of the long-stem pipet should not touch the liquid in the "NaHCO3"
pipet.
3. Release the pressure on the bulb so that it draws gas up into it.
4. Store the thin-stem “CO2” pipet (with the bulb end up) and the wide-stem
"NaHCO3" pipet (with the bulb end down) in a small beaker.
5. Repeat the gas collection procedure using the "NaHSO3" and "SO2" pipets.
6. Repeat the gas collection procedure using the "NaNO2" and "NO2" pipets.
Record Data
1. Insert the pipet labeled “CO2” into the test tube
alongside the pH electrode so that its tip extends
into the water to the bottom of the test tube.
2. Click the Start (
) button to begin recording
data. After 15 seconds, gently squeeze the bulb of
the pipet so that bubbles of CO2 slowly bubble up
through the solution. Use both hands to squeeze all
of the gas from the bulb.
• Data recording will end automatically after 100
seconds have passed.
3. Remove the pH electrode from the test tube. Dispose of the contents of the
test tube as directed by your instructor. Rinse the test tube thoroughly with
water.
4. Rinse the pH electrode thoroughly with distilled water and return it to the
test tube.
5. Put 4.0 mL of water into the test tube.
6. Repeat steps 1-5 using NO2 gas.
7. Repeat steps 1-4 using SO2 gas.
8. When you are finished, rinse the pH electrode with distilled water and return
it to the sensor storage bottle. Dispose of the pipets as directed.
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9. Acid Rain
9. Save your DataStudio file (on the File menu, click Save Activity As...) to the
location specified by your teacher.
Analyze
Record your calculations and data in the data table on the Student Response
Sheet.
1. Read the minimum and maximum values from the graph and insert the values on
the Student Response Sheet. Record the change in pH for each run in the
Student Response Sheet.
2. Answer all the questions on the Student Response Sheet.
3. Follow your teacher’s instructions regarding cleaning up your work space and
putting away equipment.
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9. Acid Rain
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Student Instruction Sheet PS-2809
RAINY DAY ACTIVITY
RAINY DAY ACTIVITY
9. Acid Rain
Student Response Sheet
Name: ______________________________
Date: ______________________________
Rainy Day Activity
Vocabulary
Use available resources to find the definitions of the following terms:
acid rain:_____________________________________________________
___________________________________________________________
acidification: __________________________________________________
___________________________________________________________
alkaline: _____________________________________________________
___________________________________________________________
buffering capacity: _____________________________________________
___________________________________________________________
dry deposition: ________________________________________________
___________________________________________________________
wet deposition: ________________________________________________
___________________________________________________________
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St udent Response Sheet 255
9. Acid Rain
RAINY DAY ACTIVITY
Predict
Which gas (carbon dioxide, nitrogen dioxide, or sulfur dioxide) will cause the
greatest change in the pH of water when it is dissolved in the water?
___________________________________________________________
___________________________________________________________
___________________________________________________________
Data
Make a sketch of your graph of pH versus Time. Label the axes and any important
parts.
Data Table
Gas
Minimum pH
Carbon dioxide
Sulfur dioxide
Nitrogen dioxide
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Student Response Sheet PS-2809
Maximum pH
Change of pH
RAINY DAY ACTIVITY
9. Acid Rain
Analyze
1. In the activity, which gas caused the smallest change in pH?
___________________________________________________________
___________________________________________________________
___________________________________________________________
2. In the activity, which gas caused the largest change in pH?
___________________________________________________________
___________________________________________________________
___________________________________________________________
Synthesize
1. Coal from western states, like Montana and Wyoming, has a lower percentage
of sulfur impurities than coal found in the eastern United States. How would
the burning of low-sulfur coal change acid rain?
___________________________________________________________
___________________________________________________________
___________________________________________________________
2. Do your results support your predictions?
___________________________________________________________
___________________________________________________________
___________________________________________________________
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9. Acid Rain
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Student Response Sheet PS-2809
RAINY DAY ACTIVITY