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.

Chapter 13 Water: Rivers of Life; Seas of

Sorrows

Daniel Fraser

University of Toledo, Toledo OH

©2004 Prentice Hall

Chemistry for Changing Times 10th editionHill/Kolb

Chapter 13 2

Water

• Chemical formula: H2O

• 2/3 of human body is water– Similar salt concentration to the ocean’s

• Only substance to exist in all three phases on Earth

• Life as we know it is dependent on water

Chapter 13 3

Properties of Water

• All properties result from its shape

• Only common liquid on planet

• Expands when frozen– Solid less dense than liquid– Lakes don’t freeze solid during winter

• High density for liquids– Oil spills float. Do not sink

Chapter 13 4

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 13 5

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 13 6

Water Cycle• ~98% salt water; ~2% polar ice caps

<1% fresh water

Chapter 13 7

Natural Contaminants

• Gases: – O2 needed by aquatic life– CO2 produces acid rain

• Dissolved solids– Hard water: contains high amounts of Ca,

Mg, and Fe

• Organic matter– Dissolved decaying matter

Chapter 13 8

Chapter 13 9

Human Contamination

• May come from home, farm, or factory

• Wastes fall into two categories– Organic– Inorganic

• Most water contamination is local

Chapter 13 10

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 13 11

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

CaCO3(s) + 2 H+ Ca2+ + CO2(g) + H2O(l)

Chapter 13 12

Sewage

• Breakdown of organic matter requires O2

– Aerobic oxidation

• Deplete dissolved oxygen in water

• Measure amount of oxidation by using biological oxygen demand (BOD)– Higher BOD, greater amount of O2 required

and more oxygen depleted from the environment

Chapter 13 13

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 13 14

• Release of a variety of different things when organic matter decays

• Depends on whether aerobic or anaerobic decay takes place– With or without O2

Chapter 13 15

Industrial Pollution• Requires lots of water to produce a car

Material Water required

(m3 water/ton of material)

Steel 100

Paper 20

Copper 400

Rayon 800

Aluminum 1280

Synthetic rubber 2400

Chapter 13 16

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 13 17

Some Groundwater Contaminants

• Nitrates, NO3–

• Come from fertilizers, decomposition of organic wastes, and animal feedlots

• Once present, difficult to remove

• Causes methemoglobinemia– Blue baby syndrome

Chapter 13 18

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 13 19

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 13 20

Chapter 13 21

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 13 22

Concentration Measurements

• Per Cent or Parts Per Hundred

• = mass of part / mass of whole X 100


• Parts Per Thousand


• Parts Per Million


Chapter 13 23


• Per Cent or Parts Per Billion


• Parts Per Trillion


Chapter 13 24


• 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 13 25



• 10 g / 100 g = 0.1

• 10 g / 100 mL = 0.1

Chapter 13 26



• 10 g / 1 L = 10 g / ( 1 L X 1,000 mL / L)

• = 10 g / 1,000 mL

• = 0.01 (mass/vol.)

Chapter 13 27



• 10 µg / 1 L = 10 µg / 1,000 mL

• = (10 µg X 1 g / 106 µg) / 1,000 mL

• = (10-5 g) / 1,000 mL

• = 10-8 (mass/vol.)

Chapter 13 28

Example 13.1 Contaminant ConcentrationsThe maximum allowable level of nitrate in drinking water set by the Environmental Protection Agency is 10 mg NO3

– 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 / 106 ) / ( 1 L X 1,000 mL / 1L) = 10-7 g / 1,000 mL = 10-10

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 NO3

–

10 mg NO3–

1000 g water

1 g water

1000 mg water

10 mg NO3–

1,000,000 mg water= 10 ppm NO3

–=x

What is the molarity of the solution in Part A? CH3-O-C(CH3)3 Form. Wt. = 88 g/mol

M = moles / Liter = (10-7 g / 88 g/mole)/ 1 L = 1.14 X 10-9 M

Exercise 13.1B

Chapter 13 29

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 13 30

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

Chapter 13 31

Chapter 13 32

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 13 33

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 13 34

Wastewater Treatment• Primary sewage treatment

– Removes some solids– Has large BOD

Chapter 13 35

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 13 36

Activated Sludge Method

• Combination of primary and secondary wastewater treatment

• Sludge must be disposed of

Chapter 13 37

Other Treatments

• Charcoal filtration: absorbs organic molecules– Charcoal must be replaced periodically

• Reverse osmosis: force water through semipermeable membrane– Requires high pressures– Expensive

Chapter 13 38

Chapter 13 39

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 13 40

Water Usage• Americans use a lot more than they think

• Try to conserve water at all times

Chapter 13 41

End of Chapter 13

Chapter 13 42

Chapter 13 43

Chapter 13 44

Chapter 13 45

Chapter 13 46

Chapter 13 47

Chapter 13 48

Chapter 13 49

Chapter 13 50

Chapter 13 51

Chapter 13 52

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.

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