Name: __________________________________________________
Unit 4 Section C
Lab: Making Acid Rain
Introduction
Have you seen any evidence of the effects of acid rain near where you live? In this investigation, you will generate some
laboratory-scale “acid rain.” You then will observe the effects this acidic solution has on a chemically reactive metal
(magnesium, Mg) and on marble (calcium carbonate, CaCO3 ). You will use chemical indicators to estimate the acidity
of the solution. Before starting, read the procedure to learn what you will need to do, note safety precautions, and plan
necessary data collecting and observations.
Procedure
1. Place a 1-g sample of sodium sulfite (Na2 SO3 ) in a test tube. Place the test tube inside a one-pint reclosable zip-seal
bag, holding it upright from outside the bag.
2. Find the Beral pipet that is filled with 6 M hydrochloric acid (HCl). (Caution: 6 M hydrochloric acid is corrosive. If
you spill it on yourself or others, wash it off thoroughly and inform your teacher. Avoid breathing any HCl fumes.)
3. Without squeezing the Beral pipet bulb, place the filled pipet, with the dropper end facing down, inside the test tube
containing sodium sulfite. Measure 10-mL distilled water with a graduated cylinder and pour it inside of the bag. Make
sure that the distilled water does not come in contact with the hydrochloric acid or sodium sulfite. Carefully smooth the
bag to force most of the air out. Close the bag with the zip-seal strip. See Figure 4.56 (page 367 of your textbook).
4. Slowly squeeze the Beral pipet through the outside of the bag so the hydrochloric acid drips onto the solid sodium
sulfite. Keep the test tube upright, so its contents do not spill out. Keep the bag sealed.
5. Allow the reaction in the test tube to proceed for 1 to 2 min, gently tapping the test tube every few seconds. After the
reaction in the test tube has stopped, gently swirl the water in the bottom of the bag for another 1 to 2 min. Do not
swirl the water so vigorously that it mixes with the contents of the test tube.
6. (Caution: Inhalation of this gas may produce irritation of the mucous membranes. Place the open bag AS
FAR AWAY AS POSSIBLE FROM YOU AS POSSIBLE!) Carefully open a top corner of the bag and, using a clean,
dry Beral pipet, transfer the water from the bottom of the bag to a clean, dry test tube labeled “A”.
7. Ask your teacher for two strips of yellow pH paper. This pH paper will turn red if dipped in an acidic solution.
On one strip, with a pipet, place one drop of distilled water. Record your observations in the data table on pg. 2.
8. Repeat Step 7, except use the solution from test tube A in place of the distilled water. Record your observations in
the data table.
9. Place two 1-cm lengths of magnesium ribbon in two separate clean, dry test tubes (one ribbon per test tube). To one
test tube (labeled “A-2”), add one full pipet of Solution A. To the other test tube, add one full pipet of distilled water.
Observe the reactions for 3 min. Record your observations in the data table.
10. To another clean, dry test tube, add one full pipet of distilled water. Add two small marble chips (or chalk;
calcium carbonate, CaCO3 ) to this test tube, and two small chips to the remaining solution in test tube “A”. Observe
the marble chips for 3 min; record your observations in the data table.
11. Dispose of all remaining solutions as directed by your teacher.
12. Wash your hands thoroughly before leaving the laboratory.
Questions on back side…
Name: __________________________________________________
Questions
1. The gas formed in the test tube by the reaction of hydrochloric acid with sodium sulfite was sulfur dioxide, SO2 .
The other products were water and NaCl(aq). Write a balanced equation, including states of matter, for the reaction that
produced SO2 gas:
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2. What effect did this gas have on the acidity of the distilled water placed inside the plastic bag? Support your answer
by referring to specific laboratory observations and test results.
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3. Write a chemical equation that shows how “acid rain” (H2 SO3 ) was produced from SO2 gas and water inside the zipseal bag.
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4. Describe how this laboratory investigation models the production of acid rain.
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5. As you know, precipitation with a pH less than 5.6 is defined as acid rain. How does the pH of your solution
compare to this value?
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6. If a liquid similar to the solution in the plastic bag moistened a marble statue or steel girders, what effect might it
have?
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7. a. Write an equation for the reaction between your “acid rain” (H2 SO3 ) and marble chips (CaCO3 ). (Hint: carbon
dioxide gas and aqueous calcium sulfite were two of the three products formed.) Include states of matter.
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b. Explain how your equation in Question 7a relates to acid rain’s effects on marble statues and building materials.
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Data Table
Distilled Water
pH paper
Magnesium ribbon
Calcium carbonate
(CaCO3 )
Observations
Acid Rain Solution