Chapter 17 Chem 102 Notes- Arrhenius definition of acids and bases-o Acid – anything that increases in concentration of H+ ions when dissolved in watero Base- anything that increases the concentration of OH- ions when dissolved in waterAcid example: HCl (aq)  H+ (aq) + Cl- (aq)Base example: NaOH(aq) +HCl (aq)  H2O (l) + NaCl (aq)- Bronsted-Lowry definition of acids and bases-o Based on proton transfer from one substance to anothero Acid- proton donor (H+)o Base- proton acceptorHCl (aq) + H2O(l)  H3O+(aq) + Cl-(aq)In the above equation: HCl acts as an acid and water is the base because HCl transfers H ions to H2O to form the hydronium ion H3O.EXAMPLES OF BRONSTED-LOWRY ACIDSo HNO3 + H2O  NO3 + H3O (HNO3 IS THE ACID)o NH4 + H20  NH3 + H30 (NH4 IS THE ACID AND A CATION)o H2PO4 + H20  HPO4 +H30 (H2PO IS THE ACID)EXAMPLES OF BRONSTED-LOWRY BASESo NH3 + H20  NH4 + OH (NH3 IS THE BASE)o CO3 + H2O  HCO3 + OH Acids such as HF, HCl, HNO3, and CHO3CO2H (acetic acid) are all capable of donating one proton and are called MONOPROTIC ACIDSOther acids that are capable of donating more than one proton are called POLYPROTIC acidsPolyprotic acid example: H2SO4 + H20  HSO4 + H3OPOLYPROTIC BASES- CAN ACCEPT MORE THAN ONE PROTONSFully deprotonated anions OF polyprotic acids ARE polyprotic bases including: SO42-, PO43-, CO32-, AND C2O42-Water can act as either a base or an acid – this is called being AMPHIPROTICIf it turns water into OH it’s a base.. if it turns water into H3O its an acidCONJUGATE ACID-BASE PAIRS- Conjugate acid-base pairo Consists of 2 species that differ from each other by the presence of one hydrogen ion Example: H2CO3 AND HCO3 compromise a conjugate acid-base pair- HCO3 is the base of the acid h2co3 and h2co3 is the conjugate acid of base hco3- EVERY REACTION BETWEEN A BRONSTED ACID AND A BRONSTED BASE INVOLVES TWO CONJUGATE ACID-BASE PAIRSWATER AND THE PH SCALETwo water molecules can interact with each other to produce a hydronium ion and a hydroxide ion by proton transfer from one water molecule to the otherAutoionization- self-ionization of water (also autoionization of water, and autodissociation of water) is an ionization reaction in pure water or an aqueous solution, in which a water molecule, H2O, loses the nucleus of one of its hydrogen atoms to become a hydroxide ion, OH− (autoionization is the cornerstone of our concepts of aqueous acid-base behavior)Water autoionization equilibrium lies far to the left sideAutoionizaion produces very low concentrations of H30 and OH ionsImportant aspects of the following equation Kw= [H30] [OH-] = 1.0 x 10 ^-14^ AT 25 DEGREES CELSIUS are:- Based on the rules for writing equilibrium constants, we do not include the concentration of water- The equilibrium constant is given a special symbol, Kw, and is known as the AUTOIONIZATION CONSTANTOF WATER- Because autoionization is the only source of hydronium and hydroxide ions in pure water, we know that H3Omust be equal to OH… electrical conductivity measurements of pure water show that H30=OH=1.0 x 10 ^-7^M at 25 degrees Celsius so Kw has a value of 1.0 x 10 ^-14^ at 25 degrees CelsiusIn water, hydronium ions and hydroxide ion concentrations are equal (water is neutral)Adding acids increase the concentration of H30 ions, so the solution is acidic. The PH of a solution is defined as the negative of the base-10 logarithm of the hydronium ion concentrationPh= -log[H30]Poh= -log[OH]USE the neg logarithms of both sides of the expression Kw=[h30][oh] Kw= 1.0x10^-14^ = [H30][OH]-log Kw= -log (1.0x10^-14^) = -log ([H30][OH])pKw= 14.00 = -log ([H30]) + (-log[OH])pKw= 14.00 = pH + pOHThe sum of the PH and POH of a solution must be equal to 14 at 25 degrees CelsiusEQUILIBRIUM CONSTANTS FOR ACIDS AND BASESOne way to define the relative strengths of a series of acids is to measure the pH of solutions of acids of equal concentration: the lower the pH, the greater the concentration of hydronium ion, the stronger the acid. For a strong monoprotic acid, H3O in solution is equal to the original acid concentration.. similarly, for a strong monoprotic bse, OH will be equal to the original base concentrationFor a weak acid H30 will be much less than the original acid concentration. That is h3o will be smaller than if the acid were a strong acid of the same concentration.. similarly, a weak base will give a smaller OH than if the base were a strong base of the same concentrationFor a series of weak monoprotic acids of the same concentration, H30 will increase and the ph will decline as the acids become stronger. Similarly for a series of weak bases, OH will inceerase and the pH will increase as the bases become strongerThe relative strength of an acid or base can also be expressed quantitatively with an equilibrium constant, often called an ionization constantA large value of K indicates that ionization products are strongly favored, whereas a small value of K indicates that reactants are favored. Strongest acids are upper left and have largest Ka values.Strongest bases are lower left and have the largest Kb values.The smaller the value of Ka, the larger the value of KbLOOK OVER PAGE 766-768The pKa of an acid is the negative log of the Ka value ( just as the pH is the negative log of the hydronium ion concentration)Ka * Kb = KwAnions that are conjugate bases of strong acids are such weak bases that they have no effect on solution pHThere are numerous basic anions and all are the conjugate bases of weak acidsThe acid-base behavior of anions of polyprotic acids depends on the extent of deprotonation. For example, a fully deprotonated anion will be basic. A partially deprotonated anion is amphiprotic. It’s behavior will depend on the other species in the reactionAlkali metal and alkaline earth cations have no measurable effect on solution pHBasic cations are conjugate bases of acidic cations Acidic cations fall into two categories: metal cations with 2 and 3 pos charges and ammonium ions . all metal cations are hydrated in water, forming ions however only when M is a 2+ or 3+ ion, particularly a transition metal ion, does the ion act as an acid.Equilibrium lies to the side of the chemical equation having the weaker acid and base because the stronger base wins out the competition for the protonAll proton transfer reactions proceed from the stronger acid and base to the weaker acid and baseTHE REACTION OF A STRONG ACID WITH A STRONG BASE- Effectively