Chapter 13 Water: Rivers of Life; Seas of Sorrows Daniel Fraser University of Toledo, Toledo OH ©2004 Prentice Hall Chemistry for Changing Times 10 th edition Hill/Kolb

Chapter 132 Water Chemical formula: H 2 O 2/3 of human body is water –Similar salt concentration to the oceans Only substance to exist in all three phases on Earth Life as we know it is dependent on water

Chapter 133 Properties of Water All properties result from its shape Only common liquid on planet Expands when frozen –Solid less dense than liquid –Lakes dont freeze solid during winter High density for liquids –Oil spills float. Do not sink

Chapter 134 Specific Heat Ability of 1 g of a substance to store heat Water has high specific heat –Acts as moderator of temperature –Do not get large temperature swings Land has low specific heat –Greater changes in temperature

Chapter 135 Heat of Vaporization Large amount of heat to vaporize a small amount of water Cool by evaporation –Sweating Land near bodies of water does have large temperature fluctuations

Chapter 136 Water Cycle ~98% salt water; ~2% polar ice caps <1% fresh water

Chapter 137 Natural Contaminants Gases: –O 2 needed by aquatic life –CO 2 produces acid rain Dissolved solids –Hard water: contains high amounts of Ca, Mg, and Fe Organic matter –Dissolved decaying matter

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9 Human Contamination May come from home, farm, or factory Wastes fall into two categories –Organic –Inorganic Most water contamination is local

Chapter 1310 Waterborne Disease Microorganisms present in all water –Cholera, typhoid fever, dysentery –Kills about 25,000 people/day Requires chemical treatment to kill them 10% of world population has access to treated water Lessens recreational value of water

Chapter 1311 Acid Rain Corrodes iron, limestone, marble >1000 bodies of water are acidified Kills by releasing metal ions into the environment Not a problem in areas where rock is limestone –Neutralizes the acid CaCO 3 (s) + 2 H + Ca 2+ + CO 2 (g) + H 2 O(l)

Chapter 1312 Sewage Breakdown of organic matter requires O 2 –Aerobic oxidation Deplete dissolved oxygen in water Measure amount of oxidation by using biological oxygen demand (BOD) –Higher BOD, greater amount of O 2 required and more oxygen depleted from the environment

Chapter 1313 Eutrophication Increase BOD when algae bloom and then die off Natural phenomenon that can be accelerated by human wastes May cause streams and lakes to no longer harbor life

Chapter 1314 Release of a variety of different things when organic matter decays Depends on whether aerobic or anaerobic decay takes place –With or without O 2

Chapter 1315 Industrial Pollution Requires lots of water to produce a car MaterialWater required (m 3 water/ton of material) Steel100 Paper20 Copper400 Rayon800 Aluminum1280 Synthetic rubber2400

Chapter 1316 Groundwater Contamination Aquifer – source of underground water –Water pumped out for human usage Water may be contaminated –Some is natural Lots of groundwater in Bangladesh contains arsenic –Contain industrial or agricultural contamination Once contaminated, hard to purify aquifer

Chapter 1317 Some Groundwater Contaminants Nitrates, NO 3 – Come from fertilizers, decomposition of organic wastes, and animal feedlots Once present, difficult to remove Causes methemoglobinemia –Blue baby syndrome

Chapter 1318 Volatile Organic Chemicals Also known as VOCs Add undesirable odor Many are suspected carcinogens Leached from buried dumps into aquifers –Very hard to remove

Chapter 1319 Underground Storage Tanks Old service stations where gasoline is stored Last about 15 years Leak gasoline as well as any additives Must be dug up and disposed of properly

Chapter 1320

Chapter 1321 Concentrations of Pollutants Typically given in parts per million, billion, or trillion –ppm, ppb, or ppt ppm means 1 g solute per 1 million grams solvent

Chapter 1322 Concentration Measurements Per Cent or Parts Per Hundred = mass of part / mass of whole X 100 = mass of part / mass of whole X 10 2 Parts Per Thousand = mass of part / mass of whole X 10 3 Parts Per Million = mass of part / mass of whole X 10 6

Chapter 1323 Concentration Measurements Per Cent or Parts Per Billion = mass of part / mass of whole X 10 9 Parts Per Trillion = mass of part / mass of whole X 10 12

Chapter 1324 Concentration Measurements Mass of Part / Mass of Whole Numerator and Denominator Must be on Same Basis, e.g students/students, people/people, politicians/politicians, grams/grams, GRAMS/MILLITERS (special situation)

Chapter 1325 Concentration Measurements Mass of Part / Mass of Whole 10 g / 100 g = g / 100 mL = 0.1

Chapter 1326 Concentration Measurements Mass of Part / Mass of Whole 10 g / 1 L = 10 g / ( 1 L X 1,000 mL / L) = 10 g / 1,000 mL = 0.01 (mass/vol.)

Chapter 1327 Concentration Measurements Mass of Part / Mass of Whole 10 µg / 1 L = 10 µg / 1,000 mL = (10 µg X 1 g / 10 6 µg) / 1,000 mL = (10 -5 g) / 1,000 mL = (mass/vol.)

Chapter 1328 Example 13.1 Contaminant Concentrations The maximum allowable level of nitrate in drinking water set by the Environmental Protection Agency is 10 mg NO 3 – per liter. What is this level expressed in ppm? What is the concentration in (a) ppb and (b) ppt corresponding to a maximum allowable level in water of 0.1 µg/L of the gasoline additive MTBE (methyl tert-butyl ether)? (0.1 µg X 1 g / 10 6 ) / ( 1 L X 1,000 mL / 1L) = g / 1,000 mL = Exercise 13.1A To convert this nitrate level to ppm, we need to have the numerator and denominator in the same units. By using m. illigrams, we make the denominator 1 million mg. The numerator then expresses the ppm of olute, that is, ppm NO 3 – 10 mg NO 3 – 1000 g water 1 g water 1000 mg water 10 mg NO 3 – 1,000,000 mg water = 10 ppm NO 3 – =x What is the molarity of the solution in Part A? CH 3 -O-C(CH 3 ) 3 Form. Wt. = 88 g/mol M = moles / Liter = (10 -7 g / 88 g/mole)/ 1 L = 1.14 X M Exercise 13.1B

Chapter 1329 Water Purification Remove dirt and most bacteria by filtration Aerate water –Otherwise tastes flat If necessary, filter through charcoal –Remove colored or odorous compounds Kill remaining bacteria

Chapter 1330 Chemical Disinfection Chlorine –Inexpensive and effective –Any remaining chlorine will kill microorganisms between water plant and house –May impart taste to water Ozone –More effective than chlorine –More expensive –No residual protection

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Chapter 1332 New Technologies for Water Purification Ultraviolet light –Kills bacteria –Effective for small-scale applications –No chemical residue Ultrasound –Tuned to produce reactive species in water –Kills bacteria –No chemical residue

Chapter 1333 Fluoride Added to water to prevent tooth decay –In areas where used, cavities decrease by up to 65% Makes tooth enamel harder Typically between 0.7–1.0 ppm In high concentrations, may cause mottling of tooth enamel

Chapter 1334 Wastewater Treatment Primary sewage treatment –Removes some solids –Has large BOD

Chapter 1335 Secondary Sewage Treatment Pass material from primary sewage treatment through sand filters Also some aeration to decrease BOD –Allow aerobic bacteria to work Typically have both primary and secondary sewage treatment for wastewater

Chapter 1336 Activated Sludge Method Combination of primary and secondary wastewater treatment Sludge must be disposed of

Chapter 1337 Other Treatments Charcoal filtration: absorbs organic molecules –Charcoal must be replaced periodically Reverse osmosis: force water through semipermeable membrane –Requires high pressures –Expensive

Chapter 1338

Chapter 1339 Bottled Water Increased usage because of perception that bottled water is safer –Less rigorous testing of bottled water vs. tap water 25% of bottled water comes from municipal water supplies May have more dissolved ions than tap water

Chapter 1340 Water Usage Americans use a lot more than they think Try to conserve water at all times

Chapter 1341 End of Chapter 13

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