CAPT Embedded Task: Acid Rain
Acid rain is a dilute solution of sulfurous acid, sulfuric acid, and/or nitric acid that falls as rain
drops. The burning of fossil fuels releases sulfur oxides and nitrogen oxide into the atmosphere.
When sulfur dioxide gas (SO2(g)) reacts with water sulfurous acid (H2SO3(aq)) is formed.
Sulfuric acid (H2SO4(aq)) forms when sulfur trioxide gas (SO3(g)) reacts with water. Gaseous
nitrogen oxides (NO, NO2, N2O, N2O5) react with water to produce nitric acid (HNO3(aq)).
Common stone building materials include marble, limestone, and sandstone. Marble is a
limestone but limestone is NOT marble. Limestone is a sedimentary rock formed by the shells
of mollusks(clams, oysters, scallops, etc.) and the exoskeletons of many marine species of
protists (one-celled organisms) containing calcium carbonate and calcium hydroxide. The
limestone is formed as layers of sediment. These chemicals are pressed together under great
pressure to form solid rock. Marble is limestone that has been heated as well as subjected to
great pressure. Marble is therefore a metamorphic rock (a sedimentary rock that has been
changed by both heat and pressure). The chemical make-up of limestone and marble is quite
similar in that both contain calcium carbonate, but many limestone samples also contain calcium
hydroxide.
Sandstone is a sedimentary rock that is formed by sand (silicon dioxide or quartz) that has been
subjected to great pressure.
Your task is to determine which of the building materials is LEAST resistant to acid rain
and which building material is MOST resistant to acid rain.
MATERIALS
samples of building materials: ground marble (calcium carbonate (CaCO3);
limestone (calcium hydroxide Ca(OH)2); and sandstone (silicon dioxide, SiO2);
acid rain: we will use vinegar (HC2H3O2) since it has the same pH as acid rain (about 5.6)
spot plate
PROCEDURE
1. Prepare a Data Table for your observations.
2. Place VERY SMALL samples of each building material in separate wells.
3. Add 5 drops of “acid rain” to each well.
4. Observe and record your observations in your Data Table.
ANALYSIS
1a. Which building material is the LEAST resistant to acid rain? _____________________
b. Explain your answer in 1a.
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2a. Which building material is the MOST resistant to acid rain? ______________________
b. Explain your answer in 2a.
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