Exam Review: Ch 4 (Energy from Combustion) & Ch 6 (Neutralizing the Threat of Acid Rain)Chapter 6Acids, Bases, and Ocean Acidification1. Arrhenius Definition of Acids & Bases; Acids and Bases in Water1. Acid: Anything that reacts with water to form H3O+ (Hydronium ion)1. The hydronium ions are the actual acid molecules2. Base: Anything that reacts with water to form OH- (Hydroxide ion)1. The hydroxide ions are the actual base molecules2. Ions1. Cations & Anions1. Cations = positively charged ions (ie. H3O+)1. Groups 1 and 22. Anions = negatively charged ions (ie. OH-)1. Groups 5, 6, and 72. Ionization energy and Electron affinity1. Ionization energy – How easily an ion loses an electron1. Lower IE = cation, Higher IE = anion.2. Electron affinity –How easily an ion gains an electron1. Lower EA= cation, Higher EA = anion3. Periodic properties and Ion formation1. Both Ionization energy and Electron affinity increase across a row2. Acids & Ion formation1. H+ can’t exist alone because it is too reactive, so it forms H3O+ in water3. Bases & Ion formation1. There is an indirect formation of OH-1. NH4 + H2O  NH4- + OH- ie. Ammonia takes a proton from water, making NH4+ and OH- . In this case, water acts as an acid.4. Conjugate Acids & Bases1. Conjugate acid-base pair – 2 substances whose formulas only differ by an H+ ionExam Review: Ch 4 (Energy from Combustion) & Ch 6 (Neutralizing the Threat of Acid Rain)1. Conjugate acid- Formed by a gain of H+ to base2. Conjugate base- Formed by loss of H+ from acid4. Polyatomic Ions – Ions with more than one atom1. 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-)3. Self-Dissociation of Water1. H2O + H2O  H3O+ + OH-1. This reaction is constantly happening (autohydrolysis) in any water (ie. Water in a water bottle.)2. For this to happen……1. Temperature must be at 25oC2. Concentrations of both H3O+ and OH- must be 1 x 10-7 , making the total concentration of ions 1 x 10-141. This is called the “autohydrolysis constant of water”, also known as Kw = 1 x 10-141. Kw can be used to find ion concentration or pH 1. See “Sample Calculations, Exam 2” #1 on Blackboard to see how this is done4. The pH scale1. Ranges from 1-14, with 1 being most acidic, 7 being neutral, and 14 being most basic2. To find pH, the product of concentrations of both H3O+ and OH- must be 1 x 10-141. Neutral solutions will have concentrations of both H3O+ and OH- at 1 x 10-72. Acidic solutions: H3O+ > 1 x 10-7 , OH- < 1 x 10-73. Basic solutions:: H3O+ < 1 x 10-7 , OH- > 1 x 10-73. pH = -[H3O+] … ie. If the concentration of H3O+ is 1 x 10-5, then pH = -(1x10-5) so pH = 55. Acid and Base Strength1. Strong Acids give up H+ easily and have 100% dissociation in water2. 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-Exam Review: Ch 4 (Energy from Combustion) & Ch 6 (Neutralizing the Threat of Acid Rain)2. Examples:1. Strong Acids: HCl, HF, HBr, HI (Hydrogen + other group 7 elements)2. Weak Acids: Formic acid, acetic acid, and most other organic acids3. Strong Bases: NaOH, LiOH, KOH, RbOH (Hydroxide + other group 1 elements)4. Weak Bases: NH3 and other combinations of ammonia2. Acid Dissociation Constants1. Measure of acid strength; Ka . The bigger the Ka , the more hydronium in the acid1. Strong acids have Ka > 1, Weak acids have Ka < 11. Most organic acids have Ka near 10-5, proving them weak6. The Acidity of Rain; Acid Rain1. Normal rain is acidic1. CO2 in atmosphere slightly dissolves in water and reacts to produce slightly carbonic acid (H2CO3)1. Acid Rain comes from oxides of sulfur and nitrogen (aka SOx and NOx)1. Most found in eastern third of US due to industrialization2. Normal ocean water is basic1. This is due to CaCO3 (Calcium carbonate)7. Ocean Acidification1. Lowering of ocean pH from increased atmospheric CO22. 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 dissolve3. Carbonate is taken from other materials in the ocean & dissolved in order to replace the carbonate in step 2 1. -This is usually taken from CaCO3, which is what keeps the ocean basic, therefore raising acidity2. See Figure 6.6 on page 251 or lecture notes for diagram3. Effects of CO2 dissolution in the oceanExam Review: Ch 4 (Energy from Combustion) & Ch 6 (Neutralizing the Threat of Acid Rain)1. Eventual dissolving of shells of sea creatures, coral and other sea plants dying, damage to reefs which will cause the loss of marine lifeChapter 4Energy from Fossil Fuels1. Electricity Generation1. Coal powered, steam turbine power plant1. Coal is combusted and boils water in a high pressure system2. The steam from the water turns the turbine to create electricity2. Energy, Work, Heat, and Temperature1. Energy: capacity to do work2. Work: movement against a force3. Heat: Energy that flows from a hotter to colder object4. Temperature: Determines direction of heat flow1. Heat is a consequence of motion, Temperature is a measure of heat content.3. 1st Law of Thermodynamics & Energy conversions1. Energy cannot be created or destroyed, only converted into another type of energy2. Application of 1st law in Turbines-1. Potential Energy- Stored in bonds of fossil fuels2. Kinetic Energy- Motion of steam molecules3. Mechanical Energy- Movement of Turbines4. Electrical Energy- Created by the Turbine3. Power plants are inefficient.2. Coal1. Consumption1. US- owns over ¼ of the world’s coal reserves1. Coal combustion is more than half all US electricity generationExam Review: Ch 4 (Energy from Combustion) & Ch 6 (Neutralizing the Threat of Acid Rain)2. Most coal use is found in Asia2. Energy content of different types of coal1. Most energy: Anthracite2. Least energy: Wood3. Oil1. Distillation and Crude Oil fractions1. Must be distilled in a distillation tower before use2. Separated into sections of tower based on amount of carbon atoms in the oil2. Use1. 1 barrel of oil = 42 gallons1. 87% used in transportation and heating2. Other 13% used in “other products” ie. plastics3. Peak oil scenarios1. “peak oil” – when over half of the crude oil reserves are used up4. Energy