CHE 101 1st EditionExam # 2 Study Guide Chapters 16, 17, 19Chapter 16: Acids & BasesArrhenius Acid-Base Definition:Acids produce H+ ions; Bases produce OH- ions ….this is not entirely true for all substances. Example: NH3 does NOT correspond with an Arrhenius acid-base reaction thus the Brønsted-Lowry definition was created.Brønsted-Lowry Acid-Base Definition: Transfer of protons (H+)Acids donate protons(H+); Bases accept protons(H+) …..Acronym BAAD(Base Accept Acids Donate)REMEMBER that (H+) AND (H3O, Hydronium ion) are interchangeable , they have equivalent reactions!Lewis Acid-Base Definition: Defined by electron pair transferAcids accept electron pairs; Bases donate electron pairs (Bases start off with a lone pair)Conjugate Acid-Base Pairs: Conjugate refers to the addition and removal of protons from the original acid or baseConjugate BASE/Acid → Removal of a Proton Example: HNO2 (A) and NO2- (CB)Conjugate ACID/Base → Addition of a Proton Example: NH3 (B) and NH4+ (CA)Properties of Water (H2O): Boiling Point of Water is 100⁰C; Freezing Point of Water is 0⁰C; Amphiprotic (Can act as BOTH an acid and a base); Self-ionization (Reacts with itself to form ions, an Equilibrium) Thus ……. Kw = [H+][OH-] = 1*10-14 ; Neutral Solutions [H+] = [OH-] Strong/Weak Acids and Bases: Strong Acids-Bases completely (100%) ionize and dissociate (break-up) in aqueous solutions. They are also referred to as strong electrolytes.Weak Acids-Bases partially (less than 100%) ionize and dissociate in aqueous solutions. They arealso referred to as weak electrolytes and contain a mixture with their conjugate. Equilibrium exists! Strong Acids: {HCl, HBr, HI, HClO3, HClO4, HNO3, H2SO4} … Anything else is weak!!Strong Bases: {LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, Ba(OH)2, Metal Oxides and Ionic hydrides/nitrides}Common Weak Acids: {HF, HClO2, HNO2, CH3COOH} Common Weak Bases: {Amines (NH3, CH3NH2)}Dissociation Constants (Ka and Kb) are for weak acids and bases ONLY!!!HA(aq) H+(aq) + A-(aq) Ka = [H+][OH-]/[HA] Weak Acid CBB(aq) + H2O(l) BH+(aq) + OH-(aq) Kb = [BH+][OH-]/[B] Weak Base CAThe larger the K value, the stronger the acid-base. Strong acids-bases have a K value greater than 1 and weak acids-bases have a K value less than 1. Strong acids-bases produce weak conjugates.(Ka)(Kb) = KwPolyprotic Acids: Can donate more than one proton (H+) at a time; K value increases as you remove H+; Harder to lose the second and third proton Examples: H3PO4, H2SO4, H2CO3Determining if a Salt is Acidic, Basic or Neutral: Separate the salt by adding a H+ to the cation and a OH- to the anion. Stronger substance wins. IfBOTH substances are strong, the solution is neutral. If BOTH substances are weak, the larger K wins!Acid Strength is defined by: Polarity (Large Electronegativity difference), Bond Strength (Weak bonds that are easier to break = More ions in solution), Stability of Conjugate Base (More stability). R-Group, Resonance and Additional Oxygens contribute to acidity.Oxyacids: Additional oxygen atoms bounded the a central atom; As the electronegativity of the central atom increases…. Ka increases; Added oxygens cause an increase in formal chargeWhen you are deciphering between two Oxyacids, which one has a greater acid-dissociation constant…… 1. Same # of Oxygens, then look at the electronegativity of the central atom.2. Different # of oxygens, then look at the formal charge of the central atom.pH Scale: defined as the negative logarithm of the Hydrogen ion concentration. Scale: 0 to 14 ….. Basic Range [pH greater than 7]; Acidic Range [pH less than 7]; Neutral [7]pH = - log[H+] OR pOH = - log[OH-] pH + pOH = 14.00 = pKwSmaller the pH, the more acidic.Measuring pH: Litmus or pH Paper, Chemical Indicators and a pH meter.Calculating K & pH: Step 1: Write the dissociation equation and expression for the weak acid or base.Step 2: Make an ICE table. Step 3: Substitute variables containing (x) into dissociation expression, Can assume (x) is negligible if Percent Ionization is less than 5%!!!Step 4: Use formulas accordingly!Percent Ionization = [H+]Equilibrium / [HA]Initial * 100%[HA]Initial is usually formatted … 0.50 – x. Ignore the x!If the percent ionization is less than 5% then you could neglect the x when solving!Chapter 17: Other Aqueous EquilibriumCommon Ion-Effect: Similar to Le Châtelier’s Principle, Equilibrium will shif due to a common ion presented in the solution. Example: NaC2H3O2 was added to a solution of HC2H3O2 The common ion is C2H3O2- . Dissociation of a weak electrolyte decreases as a strong electrolyte containing a common ion is added.Calculations: Strong electrolytes concentration is the initial concentration of the common ion. Always write the ICE table for the weak electrolyte. Always test the Percent Ionization!!! Given: 0.50M of HF and 0.10 of NaF HF(aq) H+(aq) + F- (aq) NaF is the strong electrolyte and F- is the common ion. I 0.50 0 0.10 C - x + x + x E 0.50 – x x 0.10 + xBuffered Solutions, Capacity, and Range of pHBuffers are solutions that contain a weak acid-base and its conjugate.Buffer Capacity: amount of acid-base added before a significant pH change occursGreatest buffering capacity is dependent on higher concentrations.Buffer Range: pH range where the buffer is most effective Best buffer ranges are when the weak acid-base and its conjugate have similar concentrations. Best buffered solutions are dependent upon how close pKa is to desired pH.Natural Buffers → Human Blood (pH of 7.4) and Seawater (pH of 8.1 - 8.3)Calculating the pH of a Buffer using the Henderson-Hasselbalch Equation: pH = pKa + log [Base]/[Acid] Acid-Base Titration: pH vs. Volume of titrant added ; demonstrated by a Titration CurveEquivalence Point: Equal number of moles of acid and base reactedEndpoint: point where the indicators color changes permanently; past the equivalence pointRegions of an Strong Acid-Base Titration1. Initial pH: Low pH thus very Acidic; NO Base has been added2. Between Initial pH and Equivalence Point: Acid and Base react; Acid is in excess and Baseis limiting; pH is slowly becoming more Basic3. At Equivalence Point: Moles of Acid = Moles of Base (Completely Neutralized); pH of 7.004. After Equivalence Point: Base is in excess and Acid is completely consumed; High pH