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FSU CHM 1020 - Chapter 6

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Exam Review: Ch 4 (Energy from Combustion) & Ch 6 (Neutralizing the Threat of Acid Rain)Chapter 6Acids, Bases, and Ocean AcidificationArrhenius Definition of Acids & Bases; Acids and Bases in Wateri) Acid: Anything that reacts with water to form H3O+ (Hydronium ion)(a) The hydronium ions are the actual acid moleculesii) Base: Anything that reacts with water to form OH- (Hydroxide ion)(a) The hydroxide ions are the actual base molecules Ionsa) Cations & Anionsi) Cations = positively charged ions (ie. H3O+)(a) Groups 1 and 2ii) Anions = negatively charged ions (ie. OH-)(a) Groups 5, 6, and 7b) Ionization energy and Electron affinityi) Ionization energy – How easily an ion loses an electron(a) Lower IE = cation, Higher IE = anion.ii) Electron affinity –How easily an ion gains an electron(a) Lower EA= cation, Higher EA = anionc) Periodic properties and Ion formation(1) Both Ionization energy and Electron affinity increase across a rowii) Acids & Ion formation(a) H+ can’t exist alone because it is too reactive, so it forms H3O+ in wateriii) Bases & Ion formation(1) There is an indirect formation of OH-(a) NH4 + H2O  NH4- + OH- ie. Ammonia takes a proton from water, making NH4+ and OH- . In this case, water acts as an acid.iv) Conjugate Acids & Bases(1) Conjugate acid-base pair – 2 substances whose formulas only differ by an H+ ion(a) Conjugate acid- Formed by a gain of H+ to base(b) Conjugate base- Formed by loss of H+ from acidd) Polyatomic Ions – Ions with more than one atomi) Most are Oxygen + another element (ie. SO42-, which has 48 protons but 50 electrons)(1) Found in Water: H3O+, OH-(2) Other important Polyatomic ions: Ammonium (NH4+), Carbonate (CO32-), Bicarbonate (HCO3-)Self-Dissociation of Watera) H2O + H2O  H3O+ + OH-i) This reaction is constantly happening (autohydrolysis) in any water (ie. Water in a water bottle.)ii) For this to happen……(1) Temperature must be at 25oC(2) Concentrations of both H3O+ and OH- must be 1 x 10-7 , making the total concentration of ions 1 x 10-14(a) This is called the “autohydrolysis constant of water”, also known as Kw = 1 x 10-14(i) Kw can be used to find ion concentration or pH a. See “Sample Calculations, Exam 2” #1 on Blackboard to see how this is doneExam Review: Ch 4 (Energy from Combustion) & Ch 6 (Neutralizing the Threat of Acid Rain)The pH scalea) Ranges from 1-14, with 1 being most acidic, 7 being neutral, and 14 being most basicb) To find pH, the product of concentrations of both H3O+ and OH- must be 1 x 10-14i) Neutral solutions will have concentrations of both H3O+ and OH- at 1 x 10-7ii) Acidic solutions: H3O+ > 1 x 10-7 , OH- < 1 x 10-7iii) Basic solutions:: H3O+ < 1 x 10-7 , OH- > 1 x 10-7c) pH = -[H3O+] … ie. If the concentration of H3O+ is 1 x 10-5, then pH = -(1x10-5) so pH = 5Acid and Base Strengthi) Strong Acids give up H+ easily and have 100% dissociation in waterii) Weak Acids don’t give up H+ as easily and have less than 100% dissociation in water.(1) The same goes with Strong/Weak bases, but rather than H+, the ion being given up is OH-(2) Examples:(a) Strong Acids: HCl, HF, HBr, HI (Hydrogen + other group 7 elements)(b) Weak Acids: Formic acid, acetic acid, and most other organic acids(c) Strong Bases: NaOH, LiOH, KOH, RbOH (Hydroxide + other group 1 elements)(d) Weak Bases: NH3 and other combinations of ammoniab) Acid Dissociation Constantsi) Measure of acid strength; Ka . The bigger the Ka , the more hydronium in the acid(1) Strong acids have Ka > 1, Weak acids have Ka < 1(a) Most organic acids have Ka near 10-5, proving them weakThe Acidity of Rain; Acid Raina) Normal rain is acidici) CO2 in atmosphere slightly dissolves in water and reacts to produce slightly carbonic acid (H2CO3)(a) Acid Rain comes from oxides of sulfur and nitrogen (aka SOx and NOx)(i) Most found in eastern third of US due to industrializationb) Normal ocean water is basici) This is due to CaCO3 (Calcium carbonate)Ocean Acidificationi) Lowering of ocean pH from increased atmospheric CO2b) Carbonate System in the Ocean (1) CO2 dissolves in the ocean and forms carbonic acid (bicarbonate)(2) H3O+ from carbonic acid reacts with carbonate already in ocean, causing it to dissolve(3) Carbonate is taken from other materials in the ocean & dissolved in order to replace the carbonate in step 2 (i) -This is usually taken from CaCO3, which is what keeps the ocean basic, therefore raising acidityii) See Figure 6.6 on page 251 or lecture notes for diagramc) Effects of CO2 dissolution in the oceani) Eventual dissolving of shells of sea creatures, coral and other sea plants dying, damage to reefs which will cause the loss of marine lifeChapter 4Exam Review: Ch 4 (Energy from Combustion) & Ch 6 (Neutralizing the Threat of Acid Rain)Energy from Fossil FuelsElectricity Generationa) Coal powered, steam turbine power planti) Coal is combusted and boils water in a high pressure systemii) The steam from the water turns the turbine to create electricityb) Energy, Work, Heat, and Temperaturei) Energy: capacity to do workii) Work: movement against a forceiii) Heat: Energy that flows from a hotter to colder objectiv) Temperature: Determines direction of heat flow(a) Heat is a consequence of motion, Temperature is a measure of heat content.c) 1st Law of Thermodynamics & Energy conversionsi) Energy cannot be created or destroyed, only converted into another type of energyii) Application of 1st law in Turbines-(1) Potential Energy- Stored in bonds of fossil fuels(2) Kinetic Energy- Motion of steam molecules(3) Mechanical Energy- Movement of Turbines(4) Electrical Energy- Created by the Turbineiii) Power plants are inefficient.Coala) Consumptioni) US- owns over ¼ of the world’s coal reserves(1) Coal combustion is more than half all US electricity generationii) Most coal use is found in Asiab) Energy content of different types of coali) Most energy: Anthraciteii) Least energy: WoodOila) Distillation and Crude Oil fractionsi) Must be distilled in a distillation tower before useii) Separated into sections of tower based on amount of carbon atoms in the oilb) Usei) 1 barrel of oil = 42 gallons(1) 87% used in transportation and heating(2) Other 13% used in “other products” ie. plasticsc) Peak oil scenariosi) “peak oil” – when over half of the crude oil reserves are used upd) Energy contenti) See “Sample Calculations, Exam 2” #3 on BlackboardThe Chemistry of Gasoline; BiofuelsExam Review: Ch 4


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