Exam Review Ch 4 Energy from Combustion Ch 6 Neutralizing the Threat of Acid Rain Chapter 6 Acids Bases and Ocean Acidification Arrhenius Definition of Acids Bases Acids and Bases in Water i Acid Anything that reacts with water to form H3O Hydronium ion a The hydronium ions are the actual acid molecules ii Base Anything that reacts with water to form OH Hydroxide ion a The hydroxide ions are the actual base molecules Ions a Cations Anions i Cations positively charged ions ie H3O a Groups 1 and 2 ii Anions negatively charged ions ie OH b a Groups 5 6 and 7 Ionization energy and Electron affinity i 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 anion c Periodic properties and Ion formation 1 Both Ionization energy and Electron affinity increase across a row ii Acids Ion formation a H can t exist alone because it is too reactive so it forms H3O in water iii 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 acid d Polyatomic Ions Ions with more than one atom i Most are Oxygen another element ie SO4 2 which has 48 protons but 50 electrons 1 Found in Water H3O OH 2 Other important Polyatomic ions Ammonium NH4 Carbonate CO3 2 Bicarbonate HCO3 Self Dissociation of Water a H2O H2O H3O OH i ii For this to happen This reaction is constantly happening autohydrolysis in any water ie Water in a water bottle 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 done Exam Review Ch 4 Energy from Combustion Ch 6 Neutralizing the Threat of Acid Rain The pH scale a Ranges from 1 14 with 1 being most acidic 7 being neutral and 14 being most basic b To find pH the product of concentrations of both H3O and OH must be 1 x 10 14 i Neutral solutions will have concentrations of both H3O and OH at 1 x 10 7 ii Acidic solutions H3O 1 x 10 7 OH 1 x 10 7 iii Basic solutions H3O 1 x 10 7 OH 1 x 10 7 c pH H3O ie If the concentration of H3O is 1 x 10 5 then pH 1x10 5 so pH 5 Acid and Base Strength Strong Acids give up H easily and have 100 dissociation in water i ii 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 ammonia b Acid Dissociation Constants i 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 Rain a Normal rain is acidic i CO2 in atmosphere slightly dissolves in water and reacts to produce slightly carbonic acid H 2CO3 a Acid Rain comes from oxides of sulfur and nitrogen aka SOx and NOx i Most found in eastern third of US due to industrialization b Normal ocean water is basic i This is due to CaCO3 Calcium carbonate Ocean Acidification i Lowering of ocean pH from increased atmospheric CO2 b 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 acidity ii See Figure 6 6 on page 251 or lecture notes for diagram c Effects of CO2 dissolution in the ocean i Eventual dissolving of shells of sea creatures coral and other sea plants dying damage to reefs which will cause the loss of marine life Chapter 4 Exam Review Ch 4 Energy from Combustion Ch 6 Neutralizing the Threat of Acid Rain Energy from Fossil Fuels Electricity Generation a Coal powered steam turbine power plant i Coal is combusted and boils water in a high pressure system ii The steam from the water turns the turbine to create electricity b Energy Work Heat and Temperature i Energy capacity to do work ii Work movement against a force iii Heat Energy that flows from a hotter to colder object iv 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 conversions Energy cannot be created or destroyed only converted into another type of energy i ii 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 Turbine iii Power plants are inefficient Coal a Consumption i US owns over of the world s coal reserves 1 Coal combustion is more than half all US electricity generation ii Most coal use is found in Asia b Energy content of different types of coal i Most energy Anthracite Least energy Wood ii Oil a Distillation and Crude Oil fractions i Must be distilled in a distillation tower before use ii Separated into sections of tower based on amount of carbon atoms in the oil b Use i 1 barrel of oil 42 gallons 1 87 used in transportation and heating 2 Other 13 used in other products ie plastics c Peak oil scenarios d Energy content i i peak oil when over half of the crude oil reserves are used up See Sample Calculations Exam 2 3 on Blackboard The Chemistry of Gasoline Biofuels Exam Review Ch 4 Energy from Combustion Ch 6 Neutralizing the Threat of Acid Rain Composition of Gasoline Petroleum a Hydrocarbons b C5 to C12 group i ii Simple saturated linear hydrocarbons but not always Isomers i …