Chapter 15: Acids and Bases Part IAcid and Base DefinitionsConjugate Acid-Base PairsPowerPoint PresentationAcid EquilibriumAcid StrengthStrong Acids and BasesKa and Acid StrengthIon-product constantpH and the p-functionpH ScalepH and pOHExampleCalculate the pH of a Strong Acid SolutionCalculate the pH of a Weak Acid SolutionSlide 16Dissociation of Polyprotic AcidsStrong Base SolutionsWeak Base SolutionsChapter 15 1Chapter 15: Acids and BasesPart IGeorgia Gwinnett CollegeChem 1212KFall 2013(B. Shepler)Acid and Base Definitions21. Arrhenius Acids and Bases (1880’s) •Acid: a substance that produces H+ ions in aqueous solution. Example: HCl•Base: a substance that produces OH- ions in aqueous solution. Example NaOH2. Brønsted-Lowry Acids and Bases (1923)•Acids: donate H+. Example HCl•Bases: accept H+. Example NH3•Amphoteric: Can act as an acid or a base. Example: H2OArrhenius 1903 Nobel PrizeConjugate Acid-Base Pairs3•The concept of conjugate acid-base pairs is very important to the Bronsted-Lowry theory.–These are pairs of species that differ only in the presence or absence of a proton.•In an Acid-Base reaction:•A base accepts a proton and becomes a conjugate acid•An acid donates a proton and becomes a conjugate baseH2S (aq) + NH3 (aq)  NH4+ (aq) + HS- (aq)4CH3CO2H + H2O ↔ H3O+ + CH3CO2-Acid Equilibrium5•Competition between two bases H3O+ and HA•If HA is a much stronger acid than H3O+ the equilibrium lies far to the right.•If H3O+ is a much stronger acid than HA the equilibrium lies far to the left.HA(aq) + H2O(l) ↔ H3O+(aq) + A –(aq)HA = generic acidKa is Acid Dissociation constantAcid Strength6Acid Strength: graphical representation of the behavior of acids of different strengths in aqueous solution.A strong acid: equilibrium lies far to the rightHA + H2O  H3O+ + A –A weak acid: equilibrium lies far to the leftHA + H2O ↔ H3O+ + A –A weak acid yields a relatively strong conjugate baseStrong Acids and Bases•7 Strong Acids:•8 Strong Bases:LiOHNaOHKOH Ca(OH)2RbOH Sr(OH)2CsOH Ba(OH)2 Chapter 15 7HCl, HBr, HI, HClO4, HClO3, H2SO4, HNO3The Periodic Table of the Elements1HHydrogen1.007942HeHelium4.0033LiLithium6.9414BeBeryllium9.0121825BBoron10.8116CCarbon12.01077NNitrogen14.006748OOxygen15.99949FFluorine18.998403210NeNeon20.179711NaSodium22.98977012MgMagnesium24.305013AlAluminum26.98153814SiSilicon28.085515PPhosphorus30.97376116SSulfur32.06617ClChlorine35.452718ArArgon39.94819KPotassium39.098320CaCalcium40.07821ScScandium44.95591022TiTitanium47.86723VVanadium50.941524CrChromium51.996125MnManganese54.93804926FeIron55.84527CoCobalt58.93320028NiNickel58.693429CuCopper63.54630ZnZinc65.3931GaGallium69.72332GeGermanium72.6133AsArsenic74.9216034SeSelenium78.9635BrBromine79.90436KrKrypton83.8037RbRubidium85.467838SrStrontium87.6239YYttrium88.9058540ZrZirconium91.22441NbNiobium92.9063842MoMolybdenum95.9443TcTechnetium(98)44RuRuthenium101.0745RhRhodium102.9055046PdPalladium106.4247AgSilver107.868248CdCadmium112.41149InIndium114.81850SnTin118.71051SbAntimony121.76052TeTellurium127.6053IIodine126.9044754XeXenon131.2955CsCesium132.9054556BaBarium137.32757LaLanthanum138.905572HfHafnium178.4973TaTantalum180.947974WTungsten183.8475ReRhenium186.20776OsOsmium190.2377IrIridium192.21778PtPlatinum195.07879AuGold196.9665580HgMercury200.5981TlThallium204.383382PbLead207.283BiBismuth208.9803884PoPolonium(209)85AtAstatine(210)86RnRadon(222)87FrFrancium(223)88RaRadium(226)89AcActinium(227)104RfRutherfordium(261)105DbDubnium(262)106SgSeaborgium(263)107BhBohrium(262)108HsHassium(265)109MtMeitnerium(266)110(269)111(272)112(277)113 11458CeCerium140.11659PrPraseodymium140.9076560NdNeodymium144.2461PmPromethium(145)62SmSamarium150.3663EuEuropium151.96464GdGadolinium157.2565TbTerbium158.9253466DyDysprosium162.5067HoHolmium164.9303268ErErbium167.2669TmThulium168.9342170YbYtterbium173.0471LuLutetium174.96790ThThorium232.038191PaProtactinium231.0358892UUranium238.028993NpNeptunium(237)94PuPlutonium(244)95AmAmericium(243)96CmCurium(247)97BkBerkelium(247)98CfCalifornium(251)99EsEinsteinium(252)100FmFermium(257)101MdMendelevium(258)102NoNobelium(259)103LrLawrencium(262)1995 IUPAC masses and Approved Names from http://www.chem.qmw.ac.uk/iupac/AtWt/masses for 107-111 from C&EN, March 13, 1995, p. 35112 from http://www.gsi.de/z112e.htmlKa and Acid Strength8HA + H2O ↔ H3O+ + A –Ion-product constant9Kw = [H3O+][OH-] Autoionization of water: H2O (l) + H2O (l) ↔ H3O+ (aq) + OH- (aq)Kw = 1.0 x 10-14 (at 25oC)Kw is ion-product constantpH and the p-function10•p function is just an algebraic function•The p function is a useful means of expression the concentration of proton and hydroxide ion.pH = -log[H+]pOH = -log[OH-]•Since Ka and Kb values are so small, the p function allows them to be expressed more “neatly.”pKa = -log(Ka)pKb = -log(Kb)pH Scale11pH = -log10[H3O+]pH < 7 acidic solution[H3O+] > [OH-]pH = 7 neutral solution [H3O+] = [OH-]pH > 7 basic solution [H3O+] < [OH-]pH and pOH12•[H3O+] or [OH-] can be calculated from the pH or the pOH•Another useful relationship: pH + pOH = 14.00•It comes from the equilibrium constant for the autoionization of water, called the ion-product (constant) for water, Kw. - log Kw= H3O+[ ]OH-[ ]=1.0 x10- 14( )14.00 =pH +pOHLets make a list of all the useful equationsExample•What are [H3O+], [OH-], and pOH in a solution with a pH of 4.77?Chapter 15 13Calculate the pH of a Strong Acid Solution•Strong acids COMPLETELY dissociate. The dissociation goes to completion: all reactants are converted to products.–The [H3O+] is the same as the initial concentration of the acid.•What is the [H+], [OH-], pH, and pOH of a 0.055 M solution of HCl?Chapter 15 14Calculate the pH of a Weak Acid Solution•Weak acids do NOT dissociate completely. At equilibrium, we have significant amounts of reactant (Undissociated Acid, HA) present in the solution.–Calculating the pH is just an ICE table problem.•Hypochlorous Acid, HClO, has a pKa of 7.54. What are the[H3O+], pH, [ClO-], and [HClO] in 0.115 M HClO?Chapter 15 15Example•These acid/base problems are just more examples of all the ICE table problems we did in Chapter 14.•A 0.250 mol sample of HX is dissolved in enough water to form 655 mL of solution. If the pH of the solution is 3.54, what is the Ka of HX?Chapter 15 16Dissociation of Polyprotic Acids•Polyprotic Acids: Acids that contain more than one ionizable proton.