Chem 102 1st Edition Lecture 24Outline of Last Lecture I. AtmosphereII. Coverage Gap and OzoneOutline of Current LectureI. Acid RainII. SMOGIII. Greenhouse EffectIV. Earth’s WaterV. Water PurificationCurrent LectureI. Acid Rain- pH of 4, this is the oxidization of SO2 by O2 or O3 producing SO3 which then reacts with water to form H2SO4. pH <4 can destroy all vertebrate, most invertebrate and many microorganisms. Acids react readily with metals and carbonates. -Reducing SO2 can reduce acid rain. II. SMOG- Pollution condition where weather conditions have stagnant air mass. Smog canbe formed from sunlight reacting with vehicle exhaust (photochemical smog). -Photodissociation of NO2 initiates these rxn to produce smog. -Ozone is an undesirable pollutant in the troposphere, but is being depleted in stratosphere where it is needed. III. Greenhouse Effect- Our atmosphere protects us from harmful UV and regulates temperatures on Earth. Short UV wave sunlight reaches Earth, 39% reflected by clouds remainder absorbed by surface heating it. Heated surface emits IR radiation back and These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.without complications it is emitted back to space, with complications IR is blocked or absorbed by Earth’s atmosphere which causes air temps to rise. -Greenhouse effect increases when more greenhouse gases are present. Primary is water, maintains atmospheric temps at night by absorbing IR light from the ground and radiate it back to Earth, secondary CO2 maintains surface temps due to combustion of fossil fuels. Industrial revolution increased amounts of CO2 faster than plants can extract. -Methane (CH4)- greenhouse gas, increasing ocean temps can increasing methane release. IV. Earth’s Water- 72% on Earth, 65% in humans. Water affects environment with H-bonds, high polarity, and reactive properties. 2.8% water is freshwater, 97.2% saltwater. -Seawater is saline water, saline refers to the mass of dry salts. Average salt water salinity is 35. -Atmosphere CO2 can dissolve in water, most carbon in water is from HCO3 and CO3, creating a buffer that maintains pH. -Freshwater is very small fraction of total water on Earth. Regenerated by condensation of evaporated water on Earth. Aquifers- layers of porous rock, most freshwater is under soil in ground water. V. Water Purification- Health codes limit municipal water to a salt content of less than .05%. -Desalinization- removal of salts to make water usable: -Distillation- separate substances based on boiling point.-Osmosis- movement of solvent molecules across a semipermeable membrane, moves from low to high solute. Osmotic pressure is the pressure required to stop osmosis. -Hard water- water with relatively high Mg and Ca ions. Forms insoluble carbonates that interfere with heating properties of metals. Water softening- removing ions from water, alkaline
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