studentsampleacidbase

=Acid Rain= by A. Student

__What is acid rain?__
Normal (unpolluted) rain water is slightly acidic with a pH of about 5.6. However, air pollution (mostly from car exhaust and power plants) will react with water vapor in the air to produce acid. The extra acid makes the pH of rainwater lower. Acid rain, defined as rain with a pH lower than 5.0, causes many environmental problems. Lower pH in lakes, ponds and streams can kill fish or prevent fish eggs from hatching. Though oceans are affected less dramatically by acid rain, the overall lowering of ocean pH has affected shellfish in particular, since the shells are weakened by acid. Acid rain can damage leaves on trees, which may eventually kill them. It can also wash away nutrients from soil, injuring or killing trees and plants that depend on nutrients to survive. Acid rain also affects man-made things. The acid erodes buildings and statues made of limestone and marble, as well as paint on cars.

__Chemistry of Acid Rain__
To understand acid rain, one must understand some basic concepts about acid-base chemistry. An acid is defined as a substance that produces the hydronium ion, or H+. {include proton donor, conjugate base etc} A base is defined as a substance that produces the hydroxide ion, or OH-. Properties of acid include: sour taste, conduct electricity, react with metals, corrosive Acids and bases react in what is known as neutralization reaction. H+ and OH- combine to form water, H2O. Buffers are solutions containing weak acids and their conjugate bases. When extra H+ is added, the conjugate base reacts with it, thus preventing a dramatic change in pH. Likewise, when OH- is added, the weak acid reacts with it to prevent a change in pH. Buffer systems are important to preserving ecosystems and protecting them from effects of acid rain.

Normal rain water is slightly acidic. This is due to the fact that there is carbon dioxide, a byproduct of respiration, in the air. Carbon dioxide reacts with water to produce carbonic acid, giving normal rainwater a pH of about 5.6.

Aqueous carbonic acid dissociates into a hydronium ion and biocarbonate ion. The hydronium ion is highly reactive.

A variety of pollutants in the air, including extra CO2 from car exhaust, SO2 and nitrogen oxides from burning fossil fuels in power plants and industrial smokestacks, all react with water to produce acids (carbonic, sulfuric and nitric acids). The added levels of acid causes rain pH to drop.

__Data__
In late 2001, the pH of rain was measured across the country by the US Geological Survey. LOCATION RAIN pH Boston, MA 4.6 Los Angeles, CA 5.4 New Orleans, LA 5.1 Chicago, IL 4.6 Atlanta, GA 4.6 Overall, the data suggests that acid rain is a much bigger problem in the eastern USA than in the west. the northeastern USA has the most acidic rain in the country, while the west coast has the least acidic rain.

__What is being done?__
The parts of the country most affected by acid rain are not necessarily the regions with the worst pollution from fossil fuels. For example, weather systems can carry pollution from power plants in the midwest to the northeast. To prevent acid rain, the EPA and many states are attempting to reduce the amount of pollution released into the air. Another step being taken to protect lakes is to add ___ to create a buffer system, which prevents the acidic rain from substantially changing the pH of the lake.

__Bibliography__
http://www.epa.gov/acidrain/effects/surface_water.html http://www.epa.gov/acidrain/effects/forests.html http://water.usgs.gov/nwc/NWC/pH/html/ph.html http://dbhs.wvusd.k12.ca.us/webdocs/AcidBase/Acid-Base-Properties.html

Images from:
[|http://www.chemistry.wustl.edu/~edudev/LabTutorials/Water/FreshWater/acidrain.html]