15.2 NOTES Acid Rain and Concentration

Acid rain along with increased carbon dioxide levels are a problem from burning fuel C.1 Acid Rain Acid rain Any type of precipitation that is acidic   Fog, sleet, snow, or rain with a pH lower than 5.6, which is the average pH of natural precipitation in the absence of air pollution

Rain is normally acidic due to the reaction of carbon dioxide with water forming carbonic acid, H2CO3 This reaction is: H2 + CO2  H2CO3   There are several naturally occurring reasons for acid rain, including Volcanoes, forest fires, lightning Various other gases such as SO2, SO3, and NO2 react in similar ways to CO2

The acidity of rain varies across the country Higher acid content is found farther east, closer to manufacturing   Can be as low as pH of 4.5 or less

Impact of Acid Rain Power plants, industry, and vehicles produce CO2 that lowers pH of rain   Can kill fish eggs and other aquatic life Can remove minerals from the soil

Deterioration of buildings and monuments Buildings contain metal, limestone, or concrete that are all affected by acid rain Ancient monuments have damage due to recent industrial action reacting with the limestone (calcium carbonate, CaCO3) H2SO4 + CaCO3  CaSO4 + H2O + CO2   CaSO4 is much more soluble than CaCO3

Addressing Acid Rain It is very difficult to control acid rain because rain moves with weather patterns from west to east You can’t prevent weather from moving

Clean Air Act Amendments of 1990 Addresses acid rain   Allow maximum amount of SO2 released by plants Use lower sulfur coal Scrubbers on smokestacks, but is more expensive than coal, currently

Nitrogen oxides cause almost as many problems as carbon products released in to the atmosphere   Nitrogen oxides are formed by reactions with atmospheric nitrogen with oxygen at high temps, ie combustion engines SO2 emissions are lower, but NOx aren’t as low

ChemQuandry Why is Maine’s precipitation pH so acidic when it has very little in the way of coal power plants and few residents per square mile? Farthest east in the US and weather can dump all of its acid there

C.6 Acidity, Molar Concentration, and pH Solutions Made from two parts, the solute and the solvent The solute is dissolved by the solvent

Molar Concentration Also called molarity (M)   M = moles of solute Liters of solution

What is the molarity of a solution made from dissolving 3 What is the molarity of a solution made from dissolving 3.4 moles of NaCl in 1.7 L of water?  

The equations for this is M1V1 = M2V2 Can use different quantities to reach same concentration. Acids are typically sold in solutions with very high molarities, and can be diluted down to a lower molarity by adding water.   The equations for this is M1V1 = M2V2

How much concentrated 12 M carbonic acid is needed to make How much concentrated 12 M carbonic acid is needed to make .25 L of acid with a concentration of 5.5 M?