Chemistry Third Edition Julia Burdge Lecture PowerPoints Chapter

Chemistry Third Edition Julia Burdge Lecture PowerPoints Chapter

Chemistry Third Edition Julia Burdge Lecture PowerPoints Chapter 21 Environmental Chemistry Copyright 2012, The McGraw-Hill Compaies, Inc. Permission required for reproduction or display. 1 CHAPTER 21.1 21.2 21.3 21.4 21.5 21.6 21.7 21.8

21 Environmental Chemistry Earths Atmosphere Phenomena in the Outer Layers of the Atmosphere Depletion of Ozone in the Stratosphere Volcanoes The Greenhouse Effect Acid Rain Photochemical Smog Indoor Pollution Copyright 2014, The McGrawHill Companies, Inc. Permission required for reproduction or display. 2 21.1 21.1 Earths Earths Atmosphere

Atmosphere Topics Earths Atmosphere Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 33 21.1 21.1 Earths Earths Atmosphere Atmosphere Earths EarthsAtmosphere Atmosphere Earth is unique in having an atmosphere that is chemically active and rich in oxygen. Primitive organisms used energy from the sun to break down CO2 to obtain carbon, which they incorporated in their own

cells in a process called photosynthesis. The major by-product of photosynthesis, is oxygen. Another important source of oxygen is the photodecomposition of water vapor by UV light. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 44 21.1 21.1 Earths Earths Atmosphere Atmosphere Earths EarthsAtmosphere Atmosphere Our atmosphere consists mainly of oxygen and

nitrogen gases. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 55 21.1 21.1 Earths Earths Atmosphere Atmosphere Earths EarthsAtmosphere Atmosphere The nitrogen cycle. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

66 21.1 21.1 Earths Earths Atmosphere Atmosphere Earths EarthsAtmosphere Atmosphere The nitrogen cycle: Molecular nitrogen is a very stable molecule. Through nitrogen fixation the conversion of molecular nitrogen into nitrogen compounds atmospheric nitrogen gas is converted into nitrates and other compounds. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 77

21.1 21.1 Earths Earths Atmosphere Atmosphere Earths EarthsAtmosphere Atmosphere The nitrogen cycle: Lightening also produces nitrates from nitrogen gas Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 88 21.1 21.1 Earths Earths Atmosphere

Atmosphere Earths EarthsAtmosphere Atmosphere The nitrogen cycle: Nitric acid is converted to nitrate salts in the soil. Animals use nutrients from plants to make proteins and other essential biomolecules. Denitrification reverses nitrogen fixation to complete the cycle. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 99 21.1 21.1 Earths Earths Atmosphere Atmosphere

Earths EarthsAtmosphere Atmosphere The oxygen cycle. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 10 10 21.1 21.1 Earths Earths Atmosphere Atmosphere Earths EarthsAtmosphere Atmosphere

The oxygen cycle: Atmospheric oxygen is removed through respiration and various industrial processes, which produce carbon dioxide. Photosynthesis is the major mechanism by which molecular oxygen is regenerated from carbon dioxide and water. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11 11 21.1 21.1 Earths Earths Atmosphere Atmosphere Earths EarthsAtmosphere Atmosphere Scientists divide the

atmosphere into several different layers according to temperature variation and composition. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 12 12 21.1 21.1 Earths Earths Atmosphere Atmosphere Earths EarthsAtmosphere Atmosphere

The troposphere is the layer of the atmosphere closest to Earths surface. The troposphere is the thinnest layer, but it is where all the dramatic events of weather occur. Temperature decreases linearly with increasing altitude in this region. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13 13 21.1 21.1 Earths Earths Atmosphere Atmosphere Earths EarthsAtmosphere

Atmosphere The stratosphere consists of nitrogen, oxygen, and ozone. Air temperature increases with altitude. UV radiation from the sun triggers the formation of ozone, which prevents harmful UV rays from reaching Earths surface. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 14 14 21.1 21.1 Earths Earths Atmosphere Atmosphere Earths

EarthsAtmosphere Atmosphere In the mesosphere, the concentration of ozone and other gases is low. Temperature decreases with increasing altitude. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 15 15 21.1 21.1 Earths Earths Atmosphere Atmosphere Earths EarthsAtmosphere

Atmosphere The thermosphere, or ionosphere, is the uppermost layer of the atmosphere. The increase in temperature in is the result of the bombardment of molecular oxygen and nitrogen and atomic species by energetic particles, from the sun. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 16 16 21.2 21.2 Phenomena Phenomena in in the the Outer

Outer Layers Layers of of the the Atmosphere Atmosphere Topics Aurora Borealis and Aurora Australis The Mystery Glow of Space Shuttles Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 17 17 21.2 21.2 Phenomena Phenomena in in the the Outer

Outer Layers Layers of of the the Atmosphere Atmosphere Aurora AuroraBorealis Borealisand andAurora AuroraAustralis Australis Violent eruptions on the surface of the sun, called solar flares, result in the ejection of myriad electrons and protons into space, where provide us with spectacular celestial light shows known as auroras. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

18 18 21.2 21.2 Phenomena Phenomena in in the the Outer Outer Layers Layers of of the the Atmosphere Atmosphere Aurora AuroraBorealis Borealisand andAurora AuroraAustralis

Australis Electrons and protons collide with the molecules and atoms in Earths upper atmosphere, causing them to become ionized and electronically excited. The excited molecules and ions return to the ground state with the emission of light. An excited oxygen atom emits photons at wavelengths of 558 nm (green) and between 630 and 636 nm (red): Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 19 19 21.2 21.2 Phenomena Phenomena in in the the Outer Outer Layers

Layers of of the the Atmosphere Atmosphere Aurora AuroraBorealis Borealisand andAurora AuroraAustralis Australis The blue and violet colors result from the transition in the ionized nitrogen molecule: Aurora borealis is the name given to this phenomenon in the Northern Hemisphere. In the Southern Hemisphere, it is called aurora australis. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20

20 SAMPLE PROBLEM 21.1 The bond enthalpy of O2 is 498.7 kJ/mol. Calculate the maximum wavelength (in nm) of a photon that can cause the dissociation of an O2 molecule. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 21 SAMPLE PROBLEM 21.1 Setup The conversion steps are: Solution The energy required to dissociate one O2 molecule:

Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 22 SAMPLE PROBLEM 21.1 The energy of the photon is given by E = h Calculate the wavelength of the photon, given by = c/ as follows: Any photon with a wavelength of 240 nm or shorter can dissociate an O2 molecule. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 23 21.2 21.2

Phenomena Phenomena in in the the Outer Outer Layers Layers of of the the Atmosphere Atmosphere The TheMystery MysteryGlow Glowof ofSpace SpaceShuttles Shuttles Astronauts noticed an eerie orange glow on the outside surface of their spacecraft 300 km above

Earth. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 24 24 21.2 21.2 Phenomena Phenomena in in the the Outer Outer Layers Layers of of the the Atmosphere Atmosphere The

TheMystery MysteryGlow Glowof ofSpace SpaceShuttles Shuttles It is believed that oxygen atoms interact with NO adsorbed on the shuttles surface to form electronically excited NO2: As the NO2* leaves the shell of the spacecraft, it emits photons at a wavelength of 680 nm (orange): Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 25 25 21.3 21.3 Depletion Depletion of

of Ozone Ozone in in the the Stratosphere Stratosphere Topics Depletion of Ozone in the Stratosphere Polar Ozone Holes Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26 26 21.3 21.3 Depletion Depletion of of Ozone Ozone in in the

the Stratosphere Stratosphere Depletion Depletionof ofOzone Ozonein inthe theStratosphere Stratosphere The formation of ozone begins with the photodissociation of oxygen molecules by solar radiation The highly reactive O atoms combine with oxygen molecules to form ozone: where M is some inert substance such as N2. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 27 27

21.3 21.3 Depletion Depletion of of Ozone Ozone in in the the Stratosphere Stratosphere Depletion Depletionof ofOzone Ozonein inthe theStratosphere Stratosphere Ozone itself absorbs UV light between 200 and 300 nm: The process continues when O and O2 recombine to form O3. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 28 28 21.3 21.3 Depletion Depletion of of Ozone Ozone in in the the Stratosphere Stratosphere Depletion Depletionof ofOzone Ozonein inthe theStratosphere Stratosphere

Ozone acts as our protective shield against UV radiation. The formation and destruction of ozone is a dynamic equilibrium that maintains a constant concentration of ozone in the stratosphere. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 29 29 21.3 21.3 Depletion Depletion of of Ozone Ozone in in the the Stratosphere Stratosphere Depletion

Depletionof ofOzone Ozonein inthe theStratosphere Stratosphere Since the mid-1970s scientists have been concerned about the harmful effects of CFCs on the ozone layer. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30 30 21.3 21.3 Depletion Depletion of

of Ozone Ozone in in the the Stratosphere Stratosphere Depletion Depletionof ofOzone Ozonein inthe theStratosphere Stratosphere CFCs slowly diffuse unchanged to the stratosphere, where UV radiation causes them to decompose: The reactive chlorine atoms then undergo the following reactions: Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 31

31 21.3 21.3 Depletion Depletion of of Ozone Ozone in in the the Stratosphere Stratosphere Depletion Depletionof ofOzone Ozonein inthe theStratosphere Stratosphere The overall result is the net removal of an O3 molecule from the stratosphere:

The Cl atom plays the role of a catalyst. One Cl atom can destroy up to 100,000 O3 molecules! Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 32 32 21.3 21.3 Depletion Depletion of of Ozone Ozone in in the the Stratosphere Stratosphere Depletion Depletionof ofOzone

Ozonein inthe theStratosphere Stratosphere The concentration of O3 decreases in regions that have high amounts of ClO. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 33 33 21.3 21.3 Depletion Depletion of of Ozone Ozone in in the the Stratosphere Stratosphere

Depletion Depletionof ofOzone Ozonein inthe theStratosphere Stratosphere Another group of compounds that can destroy stratospheric ozone are the nitrogen oxides, generally denoted as NOx. NO is the catalyst and NO2 is the intermediate. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 34 34 21.3 21.3 Depletion Depletion of

of Ozone Ozone in in the the Stratosphere Stratosphere Polar PolarOzone OzoneHoles Holes An Antarctic ozone hole develops in late winter, depleting the stratospheric ozone over Antarctica by as much as 50 percent. Depletion of ozone shown in blue. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 35 35

21.3 21.3 Depletion Depletion of of Ozone Ozone in in the the Stratosphere Stratosphere Polar PolarOzone OzoneHoles Holes A stream of air known as the polar vortex circles Antarctica in winter. Air trapped within this vortex becomes extremely cold during the polar night. This leads to the formation of ice particles known as

polar stratospheric clouds (PSCs). Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 36 36 21.3 21.3 Depletion Depletion of of Ozone Ozone in in the the Stratosphere Stratosphere Polar PolarOzone OzoneHoles Holes

PSCs provide a surface for reactions converting HCl and ClNO2 to more reactive chlorine molecules: By early spring, the sunlight splits molecular chlorine into chlorine atoms, which then attack ozone. The situation is not as severe in the warmer Arctic region, where the vortex does not persist quite as long. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 37 37 21.3 21.3 Depletion Depletion of of Ozone Ozone in in the the Stratosphere

Stratosphere Polar PolarOzone OzoneHoles Holes Nations throughout the world have acknowledged the need to drastically curtail or totally stop the production of CFCs. An intense effort is under way to find CFC substitutes that are not harmful to the ozone layer. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 38 38 21.4 21.4 Volcanoes Volcanoes Topics

Volcanoes Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 39 39 21.4 21.4 Volcanoes Volcanoes Volcanoes Volcanoes Volcanic eruptions are instrumental in forming large parts of Earths crust. Molten rock, called magma, in the upper mantle, rises to the surface and generates volcanic eruptions.

Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 40 40 21.4 21.4 Volcanoes Volcanoes Volcanoes Volcanoes An active volcano emits gases, liquids, and solids. The gases spewed into the atmosphere include primarily N2, CO2, HCl, HF, H2S, and water vapor. Volcanoes are the source of about two-thirds of the sulfur in the air. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

41 41 21.4 21.4 Volcanoes Volcanoes Volcanoes Volcanoes At high temperatures, the hydrogen sulfide gas given off by a volcano is oxidized by air: Some of the SO2 is reduced by more H2S from the volcano to elemental sulfur and water: Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 42 42

21.4 21.4 Volcanoes Volcanoes Volcanoes Volcanoes The rest of the SO2 is released into the atmosphere, where it reacts with water to form acid rain. Aerosols given off by volcanic eruptions destroy ozone affect climate, creating a localized cooling effect. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 43 43 21.5 21.5

The The Greenhouse Greenhouse Effect Effect Topics The Greenhouse Effect Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 44 44 21.5 21.5 The The Greenhouse Greenhouse Effect Effect The

TheGreenhouse GreenhouseEffect Effect The greenhouse effect describes the trapping of heat near Earths surface by gases in the atmosphere, particularly carbon dioxide. The transfer of CO2 to and from the atmosphere is an essential part of the carbon cycle. CO2 is produced when any form of carbon or a carboncontaining compound is burned in an excess of oxygen. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 45 45 21.5 21.5 The The Greenhouse Greenhouse Effect Effect

The TheGreenhouse GreenhouseEffect Effect The carbon cycle in our global ecosystem. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 46 46 21.5 21.5 The The Greenhouse Greenhouse Effect Effect

The TheGreenhouse GreenhouseEffect Effect Sources of CO2: Carbonates can give off CO2 when heated or treated with acid: Carbon dioxide is also a by-product of the fermentation of sugar: Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 47 47 21.5 21.5 The The Greenhouse Greenhouse Effect Effect

The TheGreenhouse GreenhouseEffect Effect Sources of CO2: Animals respire and release CO2 as an end product of metabolism: Another major source of CO2 is volcanic activity. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 48 48 21.5 21.5 The The Greenhouse Greenhouse Effect

Effect The TheGreenhouse GreenhouseEffect Effect Removal of CO2: Carbon dioxide is removed from the atmosphere by photosynthetic plants and certain microorganisms: After plants and animals die, the carbon in their tissues is oxidized to CO2 and returns to the atmosphere. There is a dynamic equilibrium between atmospheric CO2 and carbonates in the oceans and lakes. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 49 49 21.5 21.5

The The Greenhouse Greenhouse Effect Effect The TheGreenhouse GreenhouseEffect Effect Much of the solar radiant energy received by Earth is in the visible region of the spectrum. Thermal radiation emitted by Earths surface is characterized by wavelengths in the IR region. The outgoing IR radiation can be absorbed by water and carbon dioxide, but not by nitrogen and oxygen. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 50 50 21.5

21.5 The The Greenhouse Greenhouse Effect Effect The TheGreenhouse GreenhouseEffect Effect The incoming radiation from the sun and the outgoing radiation from Earths surface. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 51

51 21.5 21.5 The The Greenhouse Greenhouse Effect Effect The TheGreenhouse GreenhouseEffect Effect All molecules vibrate. The energy associated with molecular vibration is quantized. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 52 52

21.5 21.5 The The Greenhouse Greenhouse Effect Effect The TheGreenhouse GreenhouseEffect Effect To absorb a photon in the IR region, the dipole moment of the molecule must change during the course of a vibration. If the molecule is homonuclear, there can be no change in the dipole moment; the molecule has a zero dipole moment. Such molecules are IR-inactive because they cannot absorb IR radiation. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 53

53 21.5 21.5 The The Greenhouse Greenhouse Effect Effect The TheGreenhouse GreenhouseEffect Effect All heteronuclear diatomic molecules are IR-active; they can absorb IR radiation because their dipole moments change. A polyatomic molecule can vibrate in more than one way. H2O is IR active

Water, for example, can vibrate in three different ways. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 54 54 21.5 21.5 The The Greenhouse Greenhouse Effect Effect The TheGreenhouse GreenhouseEffect Effect Carbon dioxide has a linear geometry and is nonpolar.

(a) no change in dipole moment (b) change in dipole moment CO is IR active Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 55 55 21.5 21.5 The The Greenhouse Greenhouse Effect Effect The TheGreenhouse GreenhouseEffect Effect Receiving a photon in the IR region, a molecule of H2O or CO2 is promoted to a higher vibrational energy level:

These excited molecules lose their excess energy either by collision with other molecules or by spontaneous emission of radiation. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 56 56 21.5 21.5 The The Greenhouse Greenhouse Effect Effect The TheGreenhouse GreenhouseEffect Effect The concentration of CO2 has been rising steadily since the turn of the century as a result of the burning of fossil fuels

petroleum, natural gas, and coal. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 57 57 21.5 21.5 The The Greenhouse Greenhouse Effect Effect The TheGreenhouse GreenhouseEffect Effect Sources of CO2 emission

The current rate of increase is more than 1 ppm by volume per year, which is equivalent to roughly 1010 tons of CO2! Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 58 58 21.5 21.5 The The Greenhouse Greenhouse Effect Effect The TheGreenhouse GreenhouseEffect Effect Other greenhouse gases

contribute to the gradual warming of the atmosphere. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 59 59 21.5 21.5 The The Greenhouse Greenhouse Effect Effect The TheGreenhouse GreenhouseEffect Effect The relative contributions of the greenhouse gases to global

warming. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 60 60 21.5 21.5 The The Greenhouse Greenhouse Effect Effect The TheGreenhouse GreenhouseEffect Effect To combat the greenhouse effect, we must lower carbon dioxide emissions. This can be done by

improving energy efficiency in automobiles households developing nonfossil fuel energy sources phasing out CFCs recovery of methane gas generated at landfills reduction of natural gas leakages preservation forests Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 61 61 SAMPLE PROBLEM 21.2 Which of the following qualify as greenhouse gases: CO, NO, NO2, Cl2, H2, Ne? Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 62

SAMPLE PROBLEM 21.2 Strategy The molecule must possess a dipole moment or some of its vibrational motions must generate a temporary dipole moment. Setup The necessary conditions rule out homonuclear diatomic molecules and atomic species. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 63 SAMPLE PROBLEM 21.2 Solution Only CO, NO, and NO2, which are all polar molecules, qualify as greenhouse gases.

Both Cl2 and H2 are homonuclear diatomic molecules, and Ne is atomic. These three species are all IR-inactive. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 64 21.6 21.6 Acid Acid Rain Rain Topics Acid Rain Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 65 65 21.6

21.6 Acid Acid Rain Rain Acid AcidRain Rain Every year acid rain causes hundreds of millions of dollars worth of damage to stone buildings and statues throughout the world. The term stone leprosy is used by some environmental chemists to describe the corrosion of stone by acid rain. Acid rain is also toxic to vegetation and aquatic life. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 66 66 21.6

21.6 Acid Acid Rain Rain Acid AcidRain Rain Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 67 67 21.6 21.6 Acid Acid Rain Rain

Acid AcidRain Rain Precipitation in the northeastern United States has an average pH of about 4.3: Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 68 68 21.6 21.6 Acid Acid Rain Rain Acid AcidRain Rain Sulfur dioxide (SO2) and, to a lesser extent, nitrogen oxides

from auto emissions are believed to be responsible for the high acidity of rainwater. Acidic oxides, such as SO2, react with water to give the corresponding acids. There are several sources of atmospheric SO2, including volcanic eruptions. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 69 69 21.6 21.6 Acid Acid Rain Rain Acid AcidRain Rain

Many metals exist combined with sulfur in nature. Extracting the metals often entails smelting, or roasting, the oresthat is, heating the metal sulfide in air to form the metal oxide and SO2. For example, The metal oxide can be reduced more easily than the sulfide to the free metal. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 70 70 21.6 21.6 Acid Acid Rain Rain Acid AcidRain Rain

The burning of fossil fuels in industry, in power plants, and in homes accounts for most of the SO2 emitted to the atmosphere. 50 million to 60 million tons of SO2 are released into the atmosphere each year! Almost all oxidized to H2SO4 in the form of aerosol, which ends up in acid rain. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 71 71 21.6 21.6 Acid Acid Rain Rain Acid

AcidRain Rain The mechanism for the conversion of SO2 to H2SO4 is quite complex and not fully understood. The reaction is believed to be initiated by the hydroxyl radical (OH): The HOSO2 radical is further oxidized to SO3: Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 72 72 21.6 21.6 Acid Acid Rain Rain Acid

AcidRain Rain The sulfur trioxide formed would then rapidly react with water to form sulfuric acid: Eventually, the acid rain can corrode limestone and marble. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 73 73 21.6 21.6 Acid Acid Rain Rain Acid AcidRain Rain

There are two ways to minimize the effects of SO2 pollution: 1. remove sulfur from fossil fuels before combustion (difficult) 2. remove SO2 as it is formed (limestone) Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 74 74 21.6 21.6 Acid Acid Rain Rain Acid AcidRain Rain Limestone is injected into the power plant boiler or furnace along with the coal.

Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 75 75 21.6 21.6 Acid Acid Rain Rain Acid AcidRain Rain At high temperatures, the following decomposition occurs: The quicklime reacts with SO2 to form calcium sulfite and some calcium sulfate: Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 76 76 21.6 21.6 Acid Acid Rain Rain Acid AcidRain Rain Quicklime is also added to lakes and soils in a process called liming to reduce their acidity. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 77 77

21.7 21.7 Photochemical Photochemical Smog Smog Topics Photochemical Smog Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 78 78 21.7 21.7 Photochemical Photochemical Smog Smog

Photochemical PhotochemicalSmog Smog The word smog was coined to describe the combination of smoke and fog that shrouded London during the 1950s. The primary cause of this noxious cloud was sulfur dioxide. Photochemical smog is formed by the reactions of automobile exhaust in the presence of sunlight. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 79 79 21.7 21.7 Photochemical Photochemical Smog Smog Photochemical

PhotochemicalSmog Smog Automobile exhaust consists mainly of NO, CO, and various unburned hydrocarbons. These gases are called primary pollutants because they set in motion a series of photochemical reactions that produce secondary pollutants. It is the secondary pollutantschiefly NO2 and O3that are responsible for the buildup of smog. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 80 80 21.7 21.7 Photochemical Photochemical Smog Smog Photochemical

PhotochemicalSmog Smog NO is the product of the reaction between atmospheric N2 and O2 at high temperatures inside an automobile engine: Nitric oxide is then oxidized to nitrogen dioxide: Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 81 81 21.7 21.7 Photochemical Photochemical Smog Smog Photochemical PhotochemicalSmog Smog

Sunlight causes the photochemical decomposition of NO2 into NO and O: Atomic oxygen is a highly reactive species that can initiate the formation of ozone: where M is some inert substance such as N2. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 82 82 21.7 21.7 Photochemical Photochemical Smog Smog Photochemical PhotochemicalSmog Smog

Ozone attacks the C=C linkage in rubber: This reaction can cause automobile tires to crack. Similar reactions are also damaging to lung tissues and other biological substances. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 83 83 21.7 21.7 Photochemical Photochemical Smog Smog Photochemical PhotochemicalSmog Smog Variations with time of primary and secondary pollutants.

Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 84 84 21.7 21.7 Photochemical Photochemical Smog Smog Photochemical PhotochemicalSmog Smog The oxidation of hydrocarbons produces various organic intermediates, which are less volatile than the hydrocarbons themselves. These substances condense into small droplets of liquid called aerosols.

This interaction makes the air look hazy. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 85 85 21.7 21.7 Photochemical Photochemical Smog Smog Photochemical PhotochemicalSmog Smog Major efforts have been made to reduce the buildup of primary pollutants. Most automobiles now are quipped with catalytic converters designed to oxidize CO and unburned hydrocarbons to CO2 and H2O and to reduce NO and NO2 to N2 and O2.

Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 86 86 21.8 21.8 Indoor Indoor Pollution Pollution Topics The Risk from Radon Carbon Dioxide and Carbon Monoxide Formaldehyde Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 87 87

21.8 21.8 Indoor Indoor Pollution Pollution The TheRisk Riskfrom fromRadon Radon Radon is a member of Group 8A (the noble gases). It is an intermediate product of the radioactive decay of uranium-238. All isotopes of radon are radioactive, but radon-222 is the most hazardous because it has the longest half-life3.8 days. Radon, is generated mostly from the phosphate minerals of uranium. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 88

88 21.8 21.8 Indoor Indoor Pollution Pollution The TheRisk Riskfrom fromRadon Radon Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 89 89 21.8 21.8

Indoor Indoor Pollution Pollution The TheRisk Riskfrom fromRadon Radon High levels of radon have been detected in homes built on reclaimed land above uranium mill tailing deposits. The colorless, odorless, and tasteless radon gas enters a building through tiny cracks in the basement floor. Radon-222 is an -emitter. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 90 90 21.8

21.8 Indoor Indoor Pollution Pollution The TheRisk Riskfrom fromRadon Radon When it decays, it produces radioactive polonium-214 and polonium-218, which can build up to high levels in an enclosed space. These solid radioactive particles are inhaled into the lungs and deposited in the respiratory tract. Over a long period of time, the particles emitted by polonium and its decay products can cause lung cancer. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 91

91 21.8 21.8 Indoor Indoor Pollution Pollution The TheRisk Riskfrom fromRadon Radon The first step combat radon pollution indoors is to measure the radon level in the basement with a reliable test kit. If the radon level is unacceptably high, then the house must be regularly ventilated. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 92 92 SAMPLE PROBLEM 21.3 The half-life of Rn-222 is 3.8 days. Starting with 1.0 g of Rn-222, how much will be left after 10 half-lives? Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 93 SAMPLE PROBLEM 21.3 Strategy All radioactive decays obey first-order kinetics, making the

half-life independent of the initial concentration. Setup Because the question involves an integral number of halflives, we can deduce the amount of Rn-222 remaining. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 94 SAMPLE PROBLEM 21.3 Solution After one half-life, the amount of Rn left is 0.5 1.0 g, or 0.5 g. After two half-lives, only 0.25 g of Rn remains. Generalizing the fraction of the isotope left after n half-lives as (1/2)n, where n = 10, we write Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 95

21.8 21.8 Indoor Indoor Pollution Pollution Carbon CarbonDioxide Dioxideand andCarbon CarbonMonoxide Monoxide Both carbon dioxide (CO2) and carbon monoxide (CO) are products of combustion. Indoor sources of these gases are gas cooking ranges woodstoves space heaters tobacco smoke human respiration exhaust fumes from cars in garages Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 96 96 21.8 21.8 Indoor Indoor Pollution Pollution Carbon CarbonDioxide Dioxideand andCarbon CarbonMonoxide Monoxide Carbon dioxide is not a toxic gas, but it does have an asphyxiating effect. Adequate ventilation is the solution to CO2 pollution. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 97 97 21.8 21.8 Indoor Indoor Pollution Pollution Carbon CarbonDioxide Dioxideand andCarbon CarbonMonoxide Monoxide CO is highly poisonous. The toxicity of CO lies in its unusual ability to bind very strongly to hemoglobin, the oxygen carrier in blood. The affinity of hemoglobin for CO is about 200 times greater than it is for O2.

The first-aid response to CO poisoning is to remove the victim immediately to an area with a plentiful oxygen supply. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 98 98 21.8 21.8 Indoor Indoor Pollution Pollution Formaldehyde Formaldehyde Formaldehyde (CH2O) is a liquid used as a preservative for laboratory specimens. Industrially, formaldehyde resins are used as bonding agents in building and furniture construction materials. Low concentrations of formaldehyde in the air can cause drowsiness, nausea, headaches, and other respiratory

ailments. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 99 99 21.8 21.8 Indoor Indoor Pollution Pollution Formaldehyde Formaldehyde Because formaldehyde is a reducing agent, devices have been constructed to remove it by means of a redox reaction. Proper ventilation is the best way to remove formaldehyde. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright 2014, The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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