Chapter 1: The Air We Breathe PDF

A Project of the American Chemical Society Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter One The Air We Breathe What is in the air that we breathe? Can air be dangerous to our health? How can understanding chemistry help us decid...

A Project of the American Chemical Society Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter One The Air We Breathe What is in the air that we breathe? Can air be dangerous to our health? How can understanding chemistry help us decide?  The Composition of Our Air It’s a mixture – a physical combination of two or more substances present in variable amounts. 1.1  Typical Composition of Inhaled and Exhaled Air Substance Inhaled Exhaled air (%)* air (%)* What’s in a Breath? Nitrogen 78.0 78.0 Oxygen 21.0 16.0 Argon 0.9 0.9 Carbon 0.04 4.0 dioxide Water vapor variable variable * Percents are by volume 1.1  Concentration Terms Parts per hundred (percent) Atmosphere is 21% oxygen = 21 oxygen molecules per 100 molecules and atoms in air Parts per million (ppm) Midday ozone levels reach about 0.4 ppm = 0.4 ozone molecules 1 x 106 molecules and atoms in air Parts per billion (ppb) Sulfur dioxide in the air should not exceed 30 ppb = 30 sulfur dioxide molecules 1 x 109 molecules and atoms in air 1.2 21% means 21 parts per hundred The means 210 parts per thousand difference between means 2,100 parts per ten thousand pph and ppm is a means 21,000 parts per hundred thousand factor of 10,000 means 210,000 parts per million Try Chapter 1 Figures Alive! for practice 1.2  The Bad Gases  Carbon monoxide  Ozone  Sulfur dioxide (SO2) and nitrogen dioxide (NO2)  Particulate matter (PM) We’ll take a closer look at each of these each in turn… 1.2  Air Pollutants: Risk Assessment Risk Assessment – evaluating scientific data and making predictions in an organized manner about the probabilities of an occurrence. Toxicity – intrinsic health hazard of a substance. Exposure – the amount of the substance encountered. Evaluate the risk of breathing the amount of ozone in the air between the hours of 4:00 p.m. and 6:00 p.m. where you live. Note: You may have to go online to access information from the EPA to help in your calculation. 1.3  Scientific Notation: A review 11000 = 1.1 x 104 0.00021 = 2.1 x 10-4 Note: same number of significant figures on 0.001021 = 1.021 x 10-3 both sides of each example. 1730 = 1.73 x 103 6.022 x 10-23 = 0.000,000,000,000,000,000,000,06022 602,200,000,000,000,000,000,000 = 6.022 x 1023 1.3 1.3 Average concentrations of air pollutants at selected locations in the U.S., in comparison with national ambient air quality standards. 1.4 1.4 EPA’s Air Quality Index Air Quality Index Levels of Health Colors (AQI) Values Concern When the AQI...air quality...as symbolized is in this range: conditions are: by this color: 050 Good Green 51–100 Moderate Yellow 101–150 Unhealthy for Orange ensitive groups 151–200 Unhealthy Red 201–300 Very unhealthy Purple 301–500 Hazardous Maroon 1.4 Figure 1.9 Air Quality Index values for Phoenix Variations reflect those in the local weather patterns. Regional events such as forest fires and volcanic eruptions can 1.4 AIRNOW Website for Local Air Quality Conditions and Forecasts 1.4 The Bird’s Nest Olympic Stadium Through Beijing Smog Winter Haze in Paris: Looking down the Champs Elysees from the top of the Arc de Triomphe Air Quality in Hawai’i Volcanoes National Park: Warning sign along crater trail  Air Quality in Hawai’i Volcanoes National Park: Halema’uma’u Crater (steam and sulfur dioxide emissions) Air Quality in Hawai’i Volcanoes National Park: Sign at Park Ranger Station Classifying Matter All Matter NO YES Can it be separated by Pure a physical process? Substances Mixtures Can it be broken NO down into YES simpler ones by chemical means? Elements Compounds 1.6  Classifying Matter Classify each of these as an element, a compound, or a mixture: carbon dioxide compound nickel element fluorine element cocaine compound compound table salt compound water soap mixture sea water mixture 1.6 Group The Periodic Table Period 1.6 A space filling model for a water molecule, H2O Oxygen atom A molecule is a fixed number of atoms held together by chemical bonds in a certain spatial arrangement. Two hydrogen atoms The chemical formula symbolically represents the type and number of each element present. 1.7  Many nonmetals occur as diatomic (made up of two atoms) molecules. H2 N2 O2 Cl2 1.7 Naming Binary Compounds Prefixes are used to designate the number of each type of element: number of atoms prefix 1 mono 2 di 3 tri 4 tetra 5 penta 6 hexa 7 hepta 8 octa 9 nona 10 deca 1.8 Naming Binary Compounds of Nonmetals Prefixes are used to designate the number of each type of element: N2O = dinitrogen monoxide (laughing gas) P2O5=diphosphorous pentoxide Notice the dropped “a” from “penta” – when both the prefix and suffix (in this case “oxide”) end and start, respectively, in a vowel, the vowel of the prefix is typically dropped; pentoxide rather than pentaoxide. 1.8 Chemical reactions are characterized by the rearrangement of atoms when reactants are transformed into products. This is an example of a C + O2 CO combustion reaction reactants product But the number of atoms on each side of the arrow must be equal (Law of Conservation of Mass). 2 C + O2 2 CO (balanced) 2 carbon atoms two carbon atoms 2 oxygen atoms two oxygen atoms 1.9 2C + O2 2 CO Another look, pictorially – using space-filling models 1.9 Balancing equations: -if an element is present in just one compound on each side, balance it first -balance anything that exists as a free element last - balance polyatomic ions as a unit - check when done – same number of atoms, and same total charge (if any) on both sides C3H8 + O2 CO2 + H2O C3H8 + 5 O2 3 CO2 + 4 H2O 3 C atoms 3 C atoms 8 H atoms 8 H atoms 10 O atoms 10 O atoms 1.9  Direct Source of Sulfur Trioxide Coal + O2 SO2 (1-3% sulfur) 2 SO2 + O2 2 SO3 Good News: Since 1985 we have seen a 55% reduction in SO2 emissions in the U.S. 1.11  Direct Source of Nitrogen Oxides High temperatures from auto engine or N2 + O2 + high temp 2 NO coal-fired power (nitrogen oxide) plant NO is very reactive: Simplified version of chemistry that occurs 2 NO + O2 2 NO2 1.11 Catalytic converters are used to catalyze the conversion of CO to CO2 The converters also reduce the amount of Volatile Organic Compounds (VOCs) from tailpipe exhaust. One reason for removing tetraethyl lead from gasoline is that the lead gunked up or poisoned the catalysts in the converters. The other reason was to reduce the amount of lead in the air. 1.11 Air Quality Index maps for Ozone Pollution, July 2006 1.12 1.12 Indoor Air Pollutants? Do you think of harmful pollutants when you light your incense candle or want to begin painting a room in the house? Why do you think these are considered indoor air pollutants? 1.13  Ozone (O3) If one breath of air contains 2 x 1022 molecules and atoms, and the acceptable ozone level is 0.12 ppm, how many molecules of O3 are in each breath? 0.12 O3 molecules 2 x 1022 molecules and atoms in a breath of air x 1 x 106 molecules and atoms in air = 2 x 1015 O3 molecules in a breath How many oxygen atoms are in each breath? 3 O atoms___ 2 x 1015 O3 molecules x = 6 x 1015 O atoms 1 O3 molecules 1.14