Environmental Chemistry 2

1. Environmental Chemistry 2

2. Acids & BasesPg.197 • Acids & bases are used everyday and within our bodies. • They are used for distinct roles & tastes. • Eg. HCL is used in your stomach for digestion (very strong acid) • Phosphoric acid is used in carbonated drinks as a flavoring agent and gives food a tangy flavor. (like cheese, jams, jelly)

3. Identifying Acids & Bases • You can identify acids & bases by: • Taste *not useful if unknown • Touch *not useful if unknown • Chemical indicator  litmus (mixture of plant compounds extracted from lichens) • Litmus turns red acid blue  base • Usually called litmus paper

4. pH Scale • pH – strength of hydrogen • pH is the strength of an acid or base • pH <7 is an acid • pH>7 is a base • pH of 7 is neutral • Every step from pH 0-14 is 0.1 times more concentrated. • Look at figure 3.9 on pg 198 of your text to see examples

5. How To Determine pH • The strength or conc. of acid determines the extent that it reacts with H2O. • You determine pH by: • The reaction changes the conductivity of H2O which can then be measured using a voltage meter. • Using pH paper – this paper changes to a characteristic color with each specific pH then the colors are matched to a chart

6. Acid Rain • Carbon,nitrogen, & sulfur produced from the burning of organic materials (contain carbon) when they react with moisture in the air to form acids. • Acid rain occurs when these compounds are washed out of the air by rain/snow. • Acid rain doesn’t look, taste or feel different

7. What does acid rain do? • Damages/destroys aquatic ecosystems (lakes & streams) • Reduces productivity of crops • Harms other vegetation • Increase the decay of buildings, structures and monuments. • Acid in soil dissolves mineral nutrients and allows them to be washed away resulting in nutrient poor soil and poor growing cond. (leaching) • Leaching may also release heavy metals (mercury, lead, nickel) into water supplies where they are consumed by plants and animals.

8. How to control acid rain • By acid/base neutralization • As a result of the ice age the glaciers moved across north america and deposited lots of calcium carbonate. This basic substance neutralizes the acid rain and therefore protects our lakes and streams. • So you add calcium carbonate to an acidic lake and you neutralize the H2O (this process is called liming) • The problem with this: once all the calcium carbonate is gone, the pH of the lake will plummet and thus negatively affect animals and plants by killing them. • Liming is very expensive • So we must try reduce or eliminate oxides in the air before they get there.

9. Catalytic Converters • These are the first step to reducing the oxides in the air leading to acid rain. • These are required on all vehicles. • They contain ceramic or honeycomb structure coated with a catalyst. • Remember a catalyst speeds up a reaction without being used up in the reaction. • The converter aids the formation of CO2 and H2O from hydrocarbons which reduces the amt of CO and NO produced. • The converter encourages complete oxidation.

10. Pollution & Pollutants • Pollutant – is any material or form of energy that will cause harm to a living organism. Basically, anything that will threaten the health or survival of that organism. • Pollution – any alteration of the environment producing a condition harmful to living things. Eg. DDT pollution • To find out if pollution is occurring you need to test on a living thing. Ie: indicator species.

11. Toxicity • The ability of a chemical to cause harm to an organism. • Acute toxicity – serious symptoms occur with one exposure. • Chronic toxicity- symptoms occur after an accumulation of a chemical to a specific level. Ie: lead, alcohol • The amt of chemical causing damage matters but can be very hard to determine. This is because of many factors ( mass, metabolism, gender) • Lethal Dose 50 is the amount of a substance that will kill 50% of the population. • Evaluate the risk of certain chemicals Pg.219-221