Lab: Making Acid Rain

Name: ______

Date: ______

Lab: Making Acid Rain

Introduction

Have you seen any evidence of the effects of acid rain near where youlive? In this investigation, you will generate some laboratory-scale“acid rain.” You then will observe the effects this acidic solution has onplant material (an apple skin), on a chemically reactive metal (magnesium,Mg), and on marble (calcium carbonate, CaCO3). You will usechemical 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.

Prelab:

Read over procedure and create a data table (qualitative – space for observations)
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 sodium chloride. Write a balanced equation for the reaction that produced SO2 gas.

3. After reading ______, discuss what happens to SO2 in the atmosphere.

Procedure

Obtain a plastic baggie and add 10mL of distilled water to the bag. Measure and record the pH of the water in the bag.
Obtain a small test tube of distilled water and record it’s pH – this will be your ‘control’ or unpolluted rain. Label the test tube “C”.
Obtain a clean glass test tube and place a 1-g sample of sodium sulfite (Na2SO3) in tube.
Carefully fill a Beral pipet with 4 M hydrochloric acid (HCl).(Caution: 4 M hydrochloric acid is corrosive. If you spill it onyourself or others, wash it off thoroughly and inform yourteacher. Avoid breathing any HCl fumes.) Without squeezing the Beral pipet bulb, place the filled pipetinside the test tube containing sodium sulfite.
Place the test tube and filled pipet inside a zip-sealed plastic baggie, holding it upright from outside the bag. Make sure thatthe distilled water does not come in contact with the hydrochloricacid or sodium sulfite. Carefully smooth the bag to force most ofthe air out. Close the bag with the zip-seal strip.
Once your bag is sealed, slowly squeeze the Beral pipet through the outside of the bagso the hydrochloric acid drips onto the solid sodiumsulfite. Keep the test tube upright, so its contents do not spillout. Keep the bag sealed.
Allow the reaction in the test tube to proceed for 1 to 2 min,gently tapping the test tube every few seconds. After the reactionin the test tube has stopped, gently swirl the water in the bottomof the bag for another 1 to 2 min. Do not swirl the water sovigorously that it mixes with the contents of the test tube.
(Caution: Avoid inhaling the gas released when you open thebag.) Carefully open a top corner of the bag and, using a clean,dry Beral pipet, transfer three pipets of water from the bottomof the bag to a clean, dry test tube. Reseal the bag. Label the testtube “A.” Measure and record the pH of the solution.
Place one drop of control water on fresh strips of pH paper. Record your observations.
Peel two pieces of fresh apple skin or a flower petal approximately 2 cm long, andplace them on a paper towel. Add 5-7 drops of liquid from testtube A to the outside of one piece of apple skin. Add 5-7 dropsof distilled water to the second piece of apple skin. (The secondapple-skin sample serves as a control. Why?). After 5 min, observethe two apple-skin samples; record your observations.
Place a 1-cm length of magnesium ribbon in a separate clean,dry test tube. Add one pipet of solution from test tube A.Observe the reaction for 3 min. Record your observations. Repeat this same procedure for the control water.
Add two small chalk chips (calcium carbonate, CaCO3) to thesolution remaining in test tube A. Observe the chalk chips for3 min; record your observations. Repeat this with the control water (record observations).
Dispose of chalk and magnesium in trashcan and rinse all test tubes out in the sink. If needed use brushes and soap to get tubes clean. Keep gloves on when cleaning out the glass test tube.
Next rinse out empty plastic baggie and hang on drying rack and then take off gloves and wash hands.
Check to make sure your area looks like how it did or better than when you started!

Post Lab Questions

1.What effect did this gas have on the acidity of the water placed inside the plastic bag? Support your answer byreferring to specific laboratory observations and test results.

2.Write a chemical equation that shows how “acid rain” (H2SO3)was produced from SO2 gas and water inside the zip-seal bag.

3.Describe how this laboratory investigation models theproduction of acid rain. In what ways does this model fall short?

4.As you know, precipitation with a pH less than 5.6 is defined asacid rain. How does the pH of your solution compare to this value?

5.If a liquid similar to the solution in the plastic bag moistened amarble statue or steel girders, what effect might it have?

6.a. Write an equation for the reaction between your “acid rain”(H2SO3) and marble chips (CaCO3). (Hint: Carbon dioxide gasand calcium sulfite solution were two of the three productsformed.)

b. Explain how your equation in Question 7a relates to acidrain’s effects on marble statues and building materials.