Acid Rain

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IntroductionJournals and Snapshots

Note: You may want to take asnapshot of the first page ofthis lab as a cover page for your Journal.

Each page of this lab that contains the symbol

should be inserted into your journal. After completing a lab page with the snapshot symbol, tap (in the upper right hand corner) to insert the page into your journal.

Acid Rain

• What makes normal rain into "acid rain"?

• What causes this phenomena and how does it relate to the chemical concept of pH?

Lab ChallengeAcid Rain

• Acid rain is a form of precipitation with an unusually low pH. The acidity causes harmful effects on the environment and living systems.

• Pollution is a primary cause of acid rain. Harmful gases produced during the burning of fossil fuels (particularly coal) interact with water in the air to form acids that become part of the precipitation.

• pH is a measurement of the concentration of hydrogen ions [H+] in water. pH values can range from 0 through 14. The lower the pH, the higher the concentration of hydrogen ions and the more acidic a substance is. A pH of 7 is neutral—neither acidic nor basic. pH values greater than 7 are considered basic.

BackgroundAcid Rain

This image is a reminder totap to take a snapshot of the page after you have entered your response.

Self-Check1. Acid rain is rainwater with an unusually low

______________.

a) particle count

b) base

c) volume

d) pH

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Background• Acid rain causes the pH of lakes and streams to drop, killing some organisms

in those environments, especially smaller organisms. Acid rain can also harm plants and other terrestrial organisms by lowering the pH of the soil.

• Acid rain accelerates the decay of building materials (such as limestone and marble), metals (such as bronze), automotive paint, and other coatings.

• The harmful pollutant gases that cause acid rain can also lower the visibility of air and make the air less healthy to breathe.

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Self-Check2. Acid rain causes the ______ of lakes to drop and

can even make statues slowly _______.

a) rise: pollute

b) pH : dissolve

c) temperature : freeze

d) number : rust

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Safety• Use all standard laboratory safety procedures.

• Do not let the hydrochloric acid (HCl) touch your skin or clothes.

• The glass pipette used to transfer HCl is fragile. Handle with care.

• Do not remove the rubber stopper from the Erlenmeyer flask once reactions have started.

• Dispose of solutions down the drain with excess water.

• After completing the lab, wash your hands with soap and water.

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Materials and EquipmentCollect all of these materials before beginning the lab.

• Sodium bicarbonate (NaHCO3), 5 g • Sodium bisulfite (NaHSO3), 5 g• Sodium nitrite (NaNO2), 1.5 g• 1 M HCl, 15 mL• Glycerin• Water or deionized water, 60 mL• Wash bottle containing distilled or

deionized water• Balance

• pH sensor• Erlenmeyer flask, 100 mL (3)• 1-hole rubber stopper for flask (3)• Glass tubing for rubber stopper• Flexible tubing to fit glass tubing, 20

cm• Beaker, 100 mL • Graduated cylinder, 25 mL• Graduated pipette and pipette bulb

Acid Rain

Sequencing Challenge

A. Determine the initial pH of a sample of distilled water.

B. Assemble the gas generator.

C. Bubble CO2 into the sample of distilled water while measuring pH.

D. Bubble NO2 into a sample of distilled water while measuring pH.

E. Bubble SO4 into a sample of distilled water while measuring pH.

Acid Rain

The steps to the left are part of the procedure for this lab activity. They are not in the right order. Determine the correct sequence of the steps, then take a snapshot of this page.

OverviewIn this lab, 3 gases will be created: CO2, NO2, and SO2. Once the gases are created, they will be bubbled through water to see how they affect pH.

• Sodium bicarbonate (NaHCO3) with hydrochloric acid (HCl) to produce carbon dioxide gas (CO2).

• Sodium nitrite (NaNO2) with hydrochloric acid (HCl) to produce nitrogen dioxide (NO2).

• Sodium bisulfite (NaHSO3) with hydrochloric acid (HCl) to produce sulfur dioxide gas (SO2).

Acid Rain

Setup: General1. Connect a pH sensor to the data collection system.

2. Measure 20.0 mL of distilled water using a graduated cylinder.

3. Pour the water into the 100 mL beaker.

4. Thoroughly rinse the pH electrode with distilled water.

5. Place the rinsed pH electrode in the beaker.

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Prediction: GeneralQ1: What do you think will happen to the pH of the water when you dissolve these

gases in it? Which gas will produce the largest change in pH?

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Setup/Collect Data: CO2 (g) and Water

1. Obtain a sample of powdered sodium bicarbonate (NaHCO3) from the teacher.

2. Measure 5 grams of NaHCO3.

3. Place the measured NaHCO3 in the Erlenmeyer flask.

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Setup/Collect Data: CO2 (g) and Water

4. Assemble the flask, stopper, glass tubing or barbed connector, and flexible tubing.

Erlenmeyer flask

pH sensorUse glycerin to lubricate the connection

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Note: If necessary, use glycerin to lubricate the connections between flexible tubing, glass connector, and rubber stopper.

Caution: Hydrochloric acid is a strong acid. Handle with care. Flush any spillage with a lot of water.

5. Add 4 mL of 1.0 M hydrochloric acid (HCl) into the Erlenmeyer flask and immediately stopper the flask.

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6. Place the free end of the flexible tubing in the water in the beaker. Immediately tap to begin recording data.

7. Record data for ~200 seconds or until the pH stabilizes. Then tap to stop recording.

Q2:What is happening to the pH of the water as you bubble CO2 into it?

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8. Determine the minimum and maximum pH* for the CO2 run and record these values in the data table on the next page.

* To Find the X- and Y-Values of a Data Point:

9. Tap to open the tools palette.

10.Tap and then tap a data point.

11.Tap or to select nearby data points.

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9. Record the minimum and maximum pH values in the data table.*

*To Enter Data into a Table: 1. Tap to open the tool

palette.2. Tap then tap a cell in

the data table to highlight it in yellow.

3. Tap to open the Keyboard screen.

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Setup/Collect Data: NO2 (g) and Water

1. Dispose of the contents in the flask and beaker from the previous trial, as directed by your teacher.

2. Thoroughly rinse the pH sensor electrode using the wash bottle.

3. Rinse the beaker and tubing with water.

4. Measure 20.0 mL of distilled water (not tap water) using a graduated cylinder.

5. Pour the water into the 40-mL beaker.

6. Thoroughly rinse the pH electrode with distilled water (not tap water).

7. Place the rinsed pH electrode in the beaker.

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Setup/Collect Data: NO2 (g) and Water

8. Measure 5 g sodium nitrite (NaNO2).

9. Place the measured NaNO2 into a clean Erlenmeyer flask.

10.Reassemble the flask, stopper, glass tubing or barbed connector, and flexible tubing (same as for CO2 run).

11.Add 4 mL of 1.0 M hydrochloric acid (HCl) into the Erlenmeyer flask and immediately stopper the flask.

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12. Place the free end of the flexible tubing in the water in the beaker. Immediately tap to begin recording data.

13. Record data for ~200 seconds or until the pH stabilizes. Then tap to stop recording.

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14. Determine the minimum and maximum pH* for the NO2 run and record these values in the data table on the next page.

* To Find the X- and Y-Values of a Data Point:

15. Tap to open the tools palette.

16. Tap and then tap a data point.

17. Tap or to select nearby data points.

15. Record the minimum and maximum pH values in the data table.*

*To Enter Data into a Table: 16. Tap to open the tools

palette.17. Tap then tap a cell in

the data table to highlight it in yellow.

18. Tap to open the Keyboard screen.

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Setup/Collect Data: SO2 (g) and Water

1. Dispose of the contents in the flask and beaker from the previous trial as directed by your teacher.

2. Thoroughly rinse the pH sensor electrode using the wash bottle.

3. Rinse the beaker, flask, and tubing with water.

4. Measure 20.0 mL of distilled water (not tap water) using a graduated cylinder.

5. Pour the water into the 40-mL beaker.

6. Thoroughly rinse the pH electrode with distilled water (not tap water).

7. Place the rinsed pH electrode in the beaker.

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Setup/Collect Data: SO2 (g) and Water

8. Measure 5 g sodium bisulfite (NaHSO3)

9. Place the measured NaHSO3 into a clean Erlenmeyer flask.

10.Reassemble the flask, stopper, glass tubing or barbed connector, and flexible tubing (same as previous runs).

11.Add 4 mL of 1.0 M hydrochloric acid (HCl) into the Erlenmeyer flask and immediately stopper the flask.

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12. Place the free end of the flexible tubing in the water in the beaker. Immediately tap to begin recording data.

13. Record data for ~200 seconds or until the pH stabilizes. Then tap to stop recording.

14. Record the minimum and maximum pH values in the data table.*

15. Calculate the change in pH for each run and record your data in the table.

*To Enter Data into a Table: 16.Tap to open the tool

palette.17.Tap then tap a cell in

the data table to highlight it in yellow.

18.Tap to open the Keyboard screen.

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Clean up1. Dispose of the contents of the flask and beaker from the previous trial as

directed by your teacher.

2. Thoroughly rinse the pH sensor electrode using the wash bottle.

3. Rinse the beaker, flask, and tubing with water.

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Analysis1. In an ideal graph of these experiments, the pH change should be dramatic

initially and then eventually level off. Why does this occur?

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2. Compare the change in pH for each type of gas tested. Which showed the greatest and least change in pH? Based on this information, which gas is worst for the environment?

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Analysis

3. In the three reactions of gas dissolving in water, what caused the reduced pH of the water?

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Analysis

Synthesis1. Which of the gases in this experiment is a man-made pollution that causes

acid rain? What are some important sources of these gases?

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Synthesis2. Coal from states in the western United States, like Montana and Wyoming, has

a lower percentage of sulfur impurities than coal found in the eastern United States. How would burning low-sulfur coal change acid rain?

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Synthesis3. What are some ways to treat the effects of acid rain?

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Synthesis4. What are some ways to PREVENT the formation of acid rain?

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Synthesis5. Although carbonic acid produces only a small decrease in pH of water, why is it

of concern in the environment?

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Multiple Choice1. Which of the following is true about acid rain?

a) Acid rain is linked to NO2 and SO2 molecules in the atmosphere.

b) Acid rain can result in the death of many species of water-dwelling organisms when it causes the pH of lakes to decrease to a level outside their tolerance.

c) Acid rain affects soil chemistry and the ability of plant roots to take in nutrients.

d) All of the above are true.

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Multiple Choice2. Which of the following play an important role

in the formation of acid rain?

a) gases in the atmosphere

b) buffers in soils and water

c) water in the atmosphere

d) A and C

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Multiple Choice3. In general, rain exerts harmful effects on ecosystems

when it falls below a pH of _______.

a) 3.6

b) 4.6

c) 5.6

d) 6.6

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4. Acid rain has been linked to which of the following?

a) Damage to fish through reactions that create high aluminum concentrations in the water.

b) Reduced nutrient uptake by tree roots.

c) Weakening trees, so they become more susceptible to other types of damage.

d) All of the above.

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Multiple Choice

You have completed the lab.Congratulations!

Please remember to follow your teacher's instructions for cleaning-up and submitting your lab.

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Images are taken from PASCO documentation, public domain clip art, or Wikimedia Foundation Commons

http://www.flickr.com/photos/buddharhubarb/21865208/http://commons.wikimedia.org/wiki/File:Acid_rain_woods1.JPGhttp://commons.wikimedia.org/wiki/File:BrownSoil.jpghttp://commons.wikimedia.org/wiki/File:FoggDam-NT.jpghttp://commons.wikimedia.org/wiki/File:Ham_Pond.jpghttp://commons.wikimedia.org/wiki/File:Sixfinger_threadfin_school.jpg

ReferencesAcid Rain