Chem 1220 Post Midterm 2
Chem 1220 Post Midterm 2 Chem 1220(Chemistry, Dr. Clark, General Chemistry)
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Chem 1220(Chemistry, Dr. Clark, General Chemistry)
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This 0 page Class Notes was uploaded by Phillip Fishbein on Sunday March 6, 2016. The Class Notes belongs to Chem 1220(Chemistry, Dr. Clark, General Chemistry) at 1 MDSS-SGSLM-Langley AFB Advanced Education in General Dentistry 12 Months taught by Dr. Clark in Winter 2016. Since its upload, it has received 15 views. For similar materials see General Chemistry in Chemistry at 1 MDSS-SGSLM-Langley AFB Advanced Education in General Dentistry 12 Months.
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Date Created: 03/06/16
Chapter 15 Chemical Equilibrium Equilibrium is where forward and reverse reactions occur at equal rates Equilibrium constant products reactants 0 Powers for each species come from coef cients in stoichiometric balanced chemical reaction 0 Written KC or Kp o Affected by temperature only Arrows going both ways in balanced equation Can use ideal gas law to change between KC and Kp Haber Process 0 Reaction to form NH3 from N2 and H2 Kp KARTquotm Pure substances are not included in equilibrium expression Adding reactions multiply their equilibrium constants Equilibria that occur entirely in the same phase are called homogeneous equilibria Lo39 and behold different phases are heterogeneous equilibria If given equilibrium constant and initial condition set up equilibrium constant expression with x o Solve for x Larger constant means reaction tends towards products Smaller means reaction tends towards reactants Predicting Direction of Reactions 0 Q is calculation for equilibrium constant using initial conditions Q gt K means reaction will move towards reactants Q lt K means reaction will move towards products Le Chatelier39s Principle 0 Describes what happens to a system in equilibrium that is disturbed Addingremoving reactants or products concentration 0 Adding reactants or removing products 0 Shifts equilibrium Ligm Removing reactants or adding products 0 Shifts equilibrium Changing pressure by changing volume changes concentration by volume Decreasing volume 0 Shifts equilibrium to side with fewer moles of gas 0 Increasing volume 0 Shifts equilibrium to side with more moles of gas Temperature changes 0 Think of heat as a reactantproduct of the reaction Exothermic or Endothermic Exothermic 0 Increasing temperature shifts equilibrium 0 Decreasing temperature shifts equilibrium Ligm Endothermic 0 Increasing temperature shifts equilibrium right 0 Decreasing temperature shifts equilibrium Chapter 16 AcidBase Equilibria Different de nitions of Acids amp Bases o Arrhenius Acid Produces H in water HCI Haq typically clusters into H3Oaq Hydronium o Arrhenius Base Produces OH39 in water NaOH 0 BronstedLowry Acid Donates a proton to another substance NH4 Has a conjugate base NH3 0 BronstedLowry Base Accepts a proton NH3 Has a conjugate acid NH4 0 Lewis Acid Electronpair acceptor BF3 0 Lewis Base Electronpair donor Hydration of ions can be considered acidbase through Lewis de nition 0 Weak acidbase is de ned by small Kc when written as reactant 0 Large Kc if written as product 0 Only acidbase reactions written in equilibrium 0 Strong Acids o HCI H2504 HNO3 HCIO3 HCIO4 HBr HI 0 All others are typically weak 0 Typically not written in equilibrium 0 Strong acid has weak conjugates Weak acids have strong conjugates Hvdroxide is not the strongest base in existence tip for future chemistry classes Acids are typically written with H on one side Autoionization of Water 0 Water selfionizes into OH39 and H3O O Kc 1014 Kg 0 Kw increases with temperature 0 AcidBase Scales 0 m logH 7for water 0 pOH ogOH39 7 for water 0 pH pOH 14 at 25 C This sum changes with temperature 0 Solutions are neutral when pH pOH 0 Strong acids and bases are strong electrolytes 0 Strong Bases 0 Alkaline and alkaline earth metals combined with CH 0 Watch for number of OH39 that dissociate from the ion 0 Highly charged ions may act as an acid and affect the pH charge of 3 Weak Acids 0 Generic Form 39 H20 H3O Ka H30A39HA pKa ogKa 0 pH affected by presence of conjugate salts EQUILIBRIUM o Polyprotic Acids Have different dissociation constants for each proton that dissociates Weak Bases 0 Generic Form A39 H20 HA OH39 Kb HAOH39A39 pr ogKb o pOH affected by presence of conjugate salts EQUILIBRIUM 0 Km corresponds to the last Ka value for conjugates of polyprotic Going Between Ka and Kb 0 Ka KW Kb 0 Kb KwKa o Kw KaKb Strong vs Weak o BronstedLowry Favorable for a strong acid to donate a proton and unfavorable to add a proton to its conjugate Favorable for a strong base to pick up a proton and unfavorable to donate the proton from its conjugate 0 Energy Easier to break apart strong acids and add a proton to a strong base Oxyacids OChem o Acids containing one or more OH bonds 0 Same number of 0H groups as oxygen atoms Acid strength increases with increasing electronegativity of the central atom Electronegativity spreads charge across molecule away from negative oxygen Increasing strength with more oxygen atoms than OH groups Helps spread charge across molecule to prevent rebonding Organic Weak Acids 0 Has a proton that can be removed 0 Has carboxyl group COOH Leads to resonance with charge position leading to more stable conjugate 0 Lower removal energy leads to stronger acid 0 Chapter 17 Additional Aspects of Aqueous Equilibria HendersonHasselbalch Equation 0 pH pKa ogX HX pKa Iogbaseacid o pOH progHXX39 pr obacidbase 0 Used for dealing with buffer solutions Adding the conjugate base to an acidic solution of a weak acid eg acetic acid with acetate Adding conjugate base to acidic solution raises pH and vice versa for base and conjugate acid 0 EQUILIBRIUM A strongweak acidbase interaction is a buffered solution Buffers resist pH change 0 Optimal buffer has base acid pH is approximately pKa o Resists pH change due to the addition of both acid and base Chapter 17 Titrations Basically acidbase equilibria and solubility investigations Ksp getting introduced Typical Titration Setup AcidBase 0 Strong base in buret 0 Acid in beaker Break titrations into 4 regions 0 Initial pH 0 Between initial pH and equivalence point 0 Equivalence point equal moles of titrant and analyte base and acid respectively 0 Post equivalence point Weak Acid and Strong Base 0 Only the same calculations for pH in post equivalence 0 Use equilibriums constants and HendersonHasselbalch equation thor equivalence point Indicators 0 Change color based on acid or base form of indicator species
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