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1 Prelim (Wks 1-6) Significant Figures Counting: 1. All nonzero digits are significant. 2. Zeroes to the left of the first nonzero digit are not significant. 3. Zeroes at the end of a number that includes a decimal point are significant. Addition and Subtraction: -the answer can contain no more decimal places than the least accurate measurement Multiplication and Division: -the answer can contain no more significant figures than the least accurate measurement Scientific Notation Addition and Subtraction numbers converted to same power of 10, coefficients added or subtracted and exponent remains Multiplication coefficients multiplied and exponents added Division coefficients divided, exponent of divisor is subtracted from exponent of number being divided J.J. Thomson cathode ray tubes discovery of electrons Bohr's View there are 2n^2 electrons allowed in a level Modern View orbitals that differ in shape and energy Filling of Orbitals: 1s2s2p3s3p4s3d4p5s 4d5p6s4f (s=2, p=6, d=10, f=14) Trends -Size of atoms decreases as you move from left to right -Size of atoms increases as you move down a group -Reactivity for metals increases as you move down a group -Reactivity for nonmetals decreases as you move down a column Groups: 1A Alkali, 2A Alkali Earths harder, more dense, 7A Halogens diatoms, 8A Noble Gases colorless, not reactive Electromagnetic Radiation: v = C , E=hv - = wavelength, v = frequency, C = speed of light -As decreases, v increases, E increases -As increases, v decreases, E decreases -Troposphere Tropopause (10 km) Stratosphere (Ozone) Mesosphere (temp decreases as you go higher in the troposphere, and then increases as you proceed through the stratosphere) -Anthropogenic pollution attributable to human activity -Clean Air Act (1990) regulates particulates, ozone, CO, nitrogen and sulfur oxides, ozone-depleting chemicals (freons) -Acid Rain H2SO4 (sulfuric acid) acidifies soil and ground water -Thermal Inversion polluted cool air can't rise above warm air Photochemical Smog formed by action of sunlight on photoreactive pollutants in the air Photodissociation of nitrogen dioxide: NO2 NO + O, O2 + O O3 (NO and NO2 are both pollutants) -RO2, NO2 and aldehydes are in smog -Incomplete combustion insufficient oxygen creates CO Solutions to Smog and Ozone -Scrub sulfur dioxide from coal emissions, cars with better mileage, electric or hydrogen, fuel cells, catalytic converters (NOX to N2), minimize volatile organic compounds -Rainout pollutants in air removed by natural precipitation -Because a double bond is stronger than a 1.5 bond and requires more energy to break, oxygen molecules absorb higher-energy UV radiation (UV-C) ozone absorbs lower energy (UV-B) therefore, ozone is more reactive toward UV light than is oxygen. -Steady state net rate of destruction = net rate of formation Chapman Cycle 1. O2 2 O 2. O + O2 O3 3. O3 O + O2 4. O + O3 2 O2 -Dobson Unit = 1 ppb of ozone in air OH and NO, both natural components of the atmosphere, can catalyze the destruction of ozone CFCs destroy ozone in the stratosphere faster than it is formed stable, nonflammable, non-corrosive, and safe to breathe -The "Ozone Hole" is over Antarctica because it is the coldest spot in Earth's atmosphere and it lacks dispersive wind currents above the pole during the winter ultimately results in the production of dangerous ozone-destroying Cl atoms confined to "hole" because of polar vortex Montreal Protocol goal was reduction and eventual end to production of substances that deplete the ozone layer -Methyl Bromide (CH3Br) used as soil fumigant mechanism of ozone depletion similar to Cl Br is even more efficient at destroying ozone phase-out under Montreal Protocol Smoking Gun Experiment ClO increase causes O3 decrease Dipole results from separation of charge over a distance **Molecule with a dipole moment will absorb infrared radiation -No net dipole when center of pos charge is also center of neg Chapter 6: Carbon Dioxide and the Greenhouse Effect -Temp at surface of Earth is determined by sun's irradiance, planet's albedo (reflection), and by the composition of the planet's atmosphere **Greenhouse Gases: Methane, Water, Carbon dioxide, CFC-12, nitrous oxide, sulfur hexafluoride, HFC's, and PFC's -Some scientists have proposed pumping carbon dioxide to the bottom of the oceans as a partial solution to global warming. -Radiational cooling enhanced loss of heat from Earth on a clear, cloudless night due to the absence of significant water vapor in the atmosphere in the form of clouds The Carbon Dioxide Cycle -problem is destroying forest and burning fossil fuels -growing plants for fuel and using that fuel is carbon neutral -burning plants and not replanting as well and burning fossil fuels is not carbon neutral -U.S., Australia, Canada have highest CO2 emission China close -Resonance structures position of valence electrons changes bonding cannot be accurately represented by a single Lewis dot structure ex. ozone **As you move from single to double to triple bonds, bond energies increase while bond lengths decrease Varenicline anti-smoking drug from Pfizer Gas forces btw molecules are small compared to energy/temp Liquids forces btw molecules are comparable Solids forces btw molecules are large -Increase in temp, concentration, contact (surface area), addition of catalyst results in increase in reaction rate -Le Chatelier's principle when a stress is applied to a system at equilibrium, the equilibrium shifts to relieve the stress **G = H - TS (If G is neg, reaction is spontaneous) -Exergonic reactions are favorable, as no input of energy is required to keep them going net energy release (-H) -Endergonic reactions are the opposite (+H) -Entropy (S)disorder large molecules often have higher entropy -Enthalpy (H) = heat **Favorable: decrease in energy and in increase in entropy Ideal Gas Law: pV = nRT p=pressure, V=volume, n=# of moles, T=temp (Kelvin), R=gas constant (0.082 liter-atmospheres / mole degrees K) Prelim 2 (Wks 7-10) 2005 US Energy Consumption = 100 Quads/yr or 100 EJ/yr or 3.2 TW The Energy Crunch to Come -Prediction is that 27.6 TW of electricity will be needed by 2050, which is more than twice the 13.5 TW we use now Estimating the Heat of Combustion - Average Bond Energies Bond Energy (KJ/Mole) C-H 416 O=O 498 C=O 803 O-H 467 C-C 356 H-H 436 C-O 336 -Energy is consumed overall - endothermic (+) -Energy is released overall exothermic (-) Calculating Heat of Combustion - if heat is put in, it's positive (reactants); if heat is given off, its negative (products) 3/7 - Petroleum -crude oil is refined by heating to 400 C in a still and the vapor goes into a distillation column more volatile portions of vapors go higher up column the larger the molecule, the lower its vapor pressure and the less distance it will travel up the column -Increase Octane rating by: -add branched chain or aromatic compounds, add octane enhancers (Tetraethyl lead, MTBE both now banned) Coal Gasification: C + H2O CO + H2 (CO is a problem) 2C +2H2O + Energy CH4 + CO2 (CO2 produced = problem) Methanol - burns more cleanly than gasoline, formaldehyde is a byproduct of combustion of it, has half the energy content of gasoline by volume, so larger fuel tanks would be necessary Alkanes: 1-Methane,2-Ethane, 3-Propane, 4-Butane, 5-Pentane, 6Hexane, 7-Heptane, 8-Octane -Cycloalkanes -C3H6 where the carbons are arranged in a triangle (cyclical hydrocarbon) is called "cyclopropane" -1-methylcyclopropene is the name for Smartfresh -Other cyclic hydrocarbons: 4 carbons = cyclobutane, 5 = cyclopentane, 6=cyclohexane (chair form or boat form) -Aromatic compounds hydrocarbons containing benzene rings most are carcinogenic -Ethers have the general formula R O R' where R and R' are alkyl groups - MTBE (methyl-tertiary-butyl ether) was used in oxygenated and reformulated gasolines -Germany is largest producer of electricity via wind power Solar Power - sun provides 250 watts/meter^2 1. Solar Heat - heat engines that use parabolic reflectors, space and water heating 2. Solar Fuel Generation photosynthesis 3. Solar Electricity Semiconductors - expensive to install Acidsreleases hydrogen (H+) ions in aqueous solution, blue litmus paper turns red in presence of acid, sour taste, acids neutralize bases H+ donor -Base provides hydroxide (OH-) ions, red litmus paper turns blue, bitter taste, neutralize acids H+ acceptor Strengths of acids and bases -determined by how completely ionized they are ex. Strong acid: HNO3 H+ + NO3 Strong base: NaOH Na+ + OHWeak acid: CH3COOH + H2O H3O+ + CH3CO2Weak base: NH3 + H2O NH4+ + OH**Water can an be acid or a base** Molarity-number of moles of solute per liter of solution pH = -log [H3O+] -Remember that log (a b) = log (a) + log (b) Another Ex: If the pH is 4.3, what is the [H3O+]? pH = -log [H3O+] = 4.3 log [H3O+] = -4.3 [H3O+] = 10^-4.3 = 5 x 10^-5 M Buffer Solutions-act as an acid-base "shock absorber" usually composed of a mixture of a weak acid and its weakly basic anion Ex: CH3COOH (aq) and CH3COO- (aq) Water-expands when it freezes, liquid at room temp due to hydrogen bonding, heat of fusion (melting) is high, high heat capacity, heat of vaporization, surface tension, excellent solvent Pollutants Found in Water 1. oxygen-demanding wastes from plants and animals 2. Infectious agents viruses and bactetria 3. Plant nutrients nitrates, phosphates from fertilizers 4. Organic chemicals 5. Heat from industry 6. Pesticides from "urban drool" runoff from lawns 7. Industrial pollutants plastics (solvents and organic Cl compounds), pesticides, medicines, petroleum products, mercury in fish, lead from paint RCRA: Resource Conservation and Recovery Act of 1976 -established the Superfund to clean up hazardous waste sites -Love Canal in Niagra, NY was first Superfund site Examples of Industrial Pollutants 1. PCB's polychlorinated biphenyls are 2 attached benzene rings that have chlorines also 2. Dioxins related to PCB's and highly toxic were used as an herbicide BOD: Biochemical Oxygen Demand is one test to look at organic material in water A. Measures the dissolved oxygen necessary for bacteria to oxidize organic compounds into normal products B. dissolved oxygen demand can fall below level needed for aquatic organisms C. Treating wastewaters in treatment plants with O2 of O3 reduces Biodegradability-Straight chain detergents can be processed by bacteria, branched chain cannot Water Purification -Primary and secondary treatments won't remove toxic metal ions, nitrates, and ammonium ions -Tertiary treatment includes filtration through carbon black to adsorb organics and treatment with denitrifying bacteria Softening Hard Water 1. Ca 2+, Mg2+, Fe3+, Mn2+ ions cause: A. Precipitations of solids in boilers, pipes, etc. B. Reaction with soap to form insoluble "curds" C. Bad tasting water 2. Lime and sodium carbonate can be added to convert Ca2+ to CaCO3 and Mg2+ to Mg(OH)2 which are less soluble in water 3. Problems: soft water is acidic (and therefore will attack the metal pipes and the solder, which if it is older will contain lead) and contains Na+, ingestion of which can correlate with heart disease 4. Most water is softened by using Ion Exchange Resins, which exchange Na+ ions for the Ca2+ and Mg2+ ions that are responsible for the water being hard A. The resin beads typically have negatively charged groups on their surface, which the Na+ ions are attracted to B. When hard water is passed through the resin beads, the more highly charged calcium ions displace the Mg ions from the surface of the beads, resulting in sodium in the softened water C. When the resins are loaded with the hard water ions, they can be refreshed through a salt-water rinse Soap--long chain hydrocarbon with ionic functional group on one end hydrocarbon portion allows it to mix and associate with oils and greases, while ionic group allows soap to be water-soluble World Water Supply 1. Aral Sea has been diminishing for past 50 yrs 2. Lake Chad in Africa has likewise shrunk significantly in past 45 yrs 3. Fish populations declining Measuring Water Purity gas chromatography, mass spectrometer, Atomic Absorption Spectroscopy Water and Environmental Justice Issues 1. UN Committee declared access to water to be a fundamental human right in 2002 2. Problem of access to water is not borne equally worldwide environmental discrimination 3. US GAO report showed that African Americans are majority pop. in 75% of locations in southeast where hazardous waste landfills are located 4. Dumping of toxic wastes in poor countries 5. Water used by industries over residents ex. Coke bottling plant in India shut down because it was "illegally and indiscriminately" using water resources 6. Women and water they spend the most time collecting it, are most affected by disease from it, and are least involved in decisions regarding its availability in their communities Oxidation-Reduction Reactions 1. Combustion reactions are oxidation reactions Oxidation = addition of oxygen, loss of electrons, or loss of hydrogen Reduction = loss of oxygen, gain of electrons, or gain of hydrogen Oxidizing Agents -gain electrons and are reduced -O2, halogens, NaOCl (bleach), H2O2 (hydrogen peroxide) Reducing Agents -lose electrons and are oxidized -often metals since they lose electrons easily -antioxidants are reducing agents, deactivating free radicals in your body **Example: CuO + H2 Cu + H2O -Cu is reduced and hydrogen is oxidized. Hydrogen is the reducing agent and oxygen is the oxidizing agent. Electrolysis: H2O + 286 KJ/mole H2(g) + 0.5 O2(g) - By applying a current to water, hydrogen gas formed at the cathode and oxygen gas formed at the anode. Fuel Cells -Produce electricity from a continuous flow of reagents. - Oxidation occurs at the anode: 2H2(g) 4H+(aq) + 4 e- Reduction occurs at the cathode: O2(g) + 4H+(aq) + 4 electrons 2H2O(g) - Net reaction: 2H2(g) + O2(g) 2H2O(g) Electrolysis is used to Produce Aluminum from aluminum oxide: reverse process is the Aluminum/Air Battery: Al + 3OH- Al(OH)3 + 3 eO2(g) + 2H2O(l) + 4 electrons 4OHOverall: 4Al + 3O2 + 6H2O 4Al(OH)3 Corrosion is an unwanted oxidation/reduction reaction. 1. Fe(s) Fe2+(aq) + 2 electrons 2. O2(g) + 2H2O(l) + 4 electrons 4OH-(aq) 3. Fe2+(aq) Fe3+ + 1 electron 4. 2Fe3+(aq) + 6OH-(aq) Fe2O3 3H2O... The rate is enhanced by salt, so winter driving of vehicles contributes to faster rusting in northern states. - To form rust oxygen, iron, and water are required. - The iron can be coated with another metal such as chromium, or zinc (galvanization). An Inconvenient Truth -Gore discusses the risk of the collapse of a major ice sheet in Greenland or in West Antarctica, either of which could raise global sea levels by approximately 20 feet (6m), flooding coastal areas and producing 100 million refugees. Meltwater from Greenland, because of its lower salinity, could halt the Gulf Stream current and quickly trigger dramatic local cooling in Northern Europe. -In an effort to explain the global warming phenomenon, the film examines annual temperature and CO2 levels for the past 600,000 years in Antarctic ice core samples. An analogy to Hurricane Katrina is used for those familiar with the 30-ft to 45-ft (9 to 14m) waves that destroyed almost a million homes in coastal Mississippi, Louisiana, and Alabama. Evidence: 1. The retreat of numerous glaciers is shown in before-andafter photographs. 2. A study by researchers at the Physics Institute at the University of Bern and the European Project for Ice Coring in Antarctic presenting data from Antarctic ice cores showing carbon dioxide concentrations higher than at any time during the past 650,000 years. 3. A 2004 survey by Dr. Naomi Oreskes of 928 peer-reviewed scientific articles on global climate change published between 1993 and 2003. The survey, published as an editorial in the journal Science, claimed that every article either supported the human-caused global warming consensus or did not comment on it. The Man in the White Suit Sidney Stratton, a brilliant and obsessed young researcher working in a textile mill. He invents an incredibly strong fiber which repels dirt and never wears out. From its fabric he makes a suit which is brilliant white because it cannot absorb dye, and slightly luminous because it includes radioactive elements. Stratton is lauded as a genius until both management and the trade union realize the consequence of his invention - once consumers have purchased enough cloth, demand will drop precipitously and put the textile industry out of business. The managers try to trick Stratton into signing away the rights to his invention but he refuses. Managers and workers each try to shut him away, but he escapes. The climax sees Stratton running through the streets at night in his glowing white suit, pursued by both the managers and the employees. As the crowd advances, his suit begins breaking apart as the chemical structure of the fibre breaks apart with time. The mob, realizing that his yarn has a flaw, rips pieces off his suit in triumph, until he is left standing in his underwear. The next day, Stratton is dismissed from his job. Departing, he consults his chemistry notes. A realization hits, and he exclaims "I see!" and strides off to perhaps try again. ... View Full Document

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