CHEM 1120 1nd EditionExam # 2 Study Guide Chapters 16 and 17Chapter 16Arrhenius acid Substance that directly yields H+ ions when dissolved in H2OEx-HCl Cl- + H+Arrhenius Base Substance that directly yields OH- ions when dissolved in H2OEx- NaOH Na+ + OH-Bronsted-Lowery Acid Donates a H+Bronsted-Lowery Base Accepts an H+Brontsted-Lowry Example NH3 (base) + H20 (acid) NH4+ (acid) + OH- (base)Conjugate acid-base pair 2 species whose formulas differ by a single H+Ex- HCN/CN- H2O /H30+Acid-base strength Strong acid=strong electrolytes disassociates 100%Stronger acid= weaker conjugate baseStronger base= weaker conjugate acidCommon strong acids HCl HclO3 HNO3 HBr HClO4 H2SO4 HICommon strong bases Hydroxides of:-Group 1A metals: LiOH, NaOH, KOHHeavy group 2A metals: Ca(OH)2, Ba(OH)2, Sr(OH)2Kw=[H+][OH-] 1.0x10^-14@25 degrees CelsiuspH=-log10[H+] 10^-ph=[H+]pKw = pH + pOH = 14 Sig figs note: 2 sig figs in log = 2 significant decimal placesKa = [H+][A-]/[HA] Acid dissociation contant, K >>> 1 = strong acid, Kb <<<1 = weak acid[H30+] = [acid] For monoprotic strong acidsPercent ionization (HX dissociated)/(HX initial) x 100Polyprotic acids 2 Ka’s, work step wiseKb = [HX][OH-]/[X-]Kw = Ka x KbpKa + pKb = 14Hydrolysis Reaction of ions with water to produce H+ or OH – ions, conjugate base of weak acid and vice versa will hydrolyzeDetermining if salt is acidic or basic 1. Identify ions formed in aqueous solution2. Assume cation and anion react with water3. Are either (or both) of these reactionsunrealistic?Predicting acid strength H-X bond polarity and strength, conjugate base stabilityMore oxygens = more acidicLewis acid Electron pair acceptorLewis base Electron pair donorChapter 17Common ion Ion common to 2 solutes, shift in equilibriumcaused by the addition of an ion already present in solutionBuffers Resist pH change when small amounts of acidor base is addedBuffer composition Weak acid + conjugate base or weak base + conjugate acidpH = pKa + log ([base]/[acid]) Henderson – Hasselbach equationChoosing acid base pair 1. Choose acid with pKa closest to desired pH2. Solve Henderson-Hasselbach equationfor [base]/[acid] ratioBuffer capacity Amount of acid or base a buffer can neutralize before pH changes significantly-more concentration buffers have higher capacity-capacity highest when concentrations of conjugates are equalTitration Accurate measurement of volume of solutionrequired to completely react with a sampleEquivalence point Point at which stoichiometrically equivalent quantities of reactant are brought togetherEnd point Point at which indicator changes color, very near equivalence pointCalculating solubility equilibria Use ICE table, molecule is dissociating Ksp = [C]^c [D]^d Solubility productFactors affecting solubility Common ion effect, pH, complex ion formation, amphotorismAmphotorism Will react in both acids and
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