Exam 3 study guide Speed is the key to do well on this exam The exam isn t any longer or shorter than the other exams but it covers a much broader range of problem types For example I won t ask you to work through a full set of titration calculations but you should be able to determine very quickly if a mixture of an acid and base is before after or at the equivalence point and solve accordingly Know this Memorize strong acids and be able to recognize them instantly HCl HBr HI HNO3 H2SO4 HClO4 Be able to convert between pH pOH H and OH Be able to convert between pKa and pKb as well as Ka and Kb using pKw and Kw pH log H H 10 pH pOH log OH OH 10 pOH pH pOH 14 00 Kw H OH Ka Kb Kw pKa log Ka pKb log Kb pKa pKb pKw General concepts and calculations Acids and conjugate bases and their salts Conjugate base of an acid is the species that remains when one proton has been removed from the acid A salt derived from a strong acid such as HCl and a weak base such as NH3 creates an acidic solution when dissolved in water Bases and conjugate acids and their salts Conjugate acid is the species that results from the addition of a proton to a base Salta derived from a strong base and weak acid produced a basic solution Amphoteric chemicals Be OH 2 Al OH 3 Sn OH 2 Pb OH 2 Cr OH 3 Cu OH 2 Zn OH 2 Cd OH 2 Can react with both acids and bases All amphoteric hydroxides are insoluble Percent ionization percent ionization ionized acid concentration at equilibrium initial concentration of acid 100 Calculate solubility molar solubility using Ksp and concentrations and vice versa solubility of compound molar solubility of compound concentrations of cations and anions Ksp of compound Ksp of compount concentrations of cations and anions molar solubility of compound solubility of compound Example 16 8 and 16 9 Titrations between Strong acid strong base Equivalence point where equimolar amounts of acid and base have been reacted pH 7 00 Weak acid strong base At equivalence point pH is greater than 7 as a result of the excess OH ions formed from the hydrolysis of the weak acid s conjugate base ex CH3COOH NaOH CH3COONa H2O simplified to CH3COOH NaOH CH3COO H2O CH3COO goes through hydrolysis CH3COO H2O CH3COOH OH Strong acid weak base pH at equivalence point is less than 7 due to hydrolysis of weak base s conjugate acid ex HCl NH3 NH4Cl simplified to H NH3 NH4 NH4 goes through hydrolysis NH4 H2O NH3 H Le Chatelier s principle and how the equilibrium is affected in different solutions Acids and salts of their conjugate bases bases and salts of their conjugate acids Creates a buffer solution which resists changes in pH Also presence of a common ion suppresses the ionization of the weak acid or base and pushes equilibrium to the elft Just salts of acids and bases Salt that produces neutral solution o Salts containing an alkali metal ion or alkaline earth metal ion and the conjugate base of a strong acid do not undergo hydrolysis to a great extent and the solutions are neutral Ex NaNO3 o Salt derived from a strong base and a weak acid creates a basic solution Ex Salt that produces basic solution CH3COONa Salt that produces acidic solution o When a salt derived from a strong acid and a weak base is dissolved in water the resulting solution is acidic o In principle all metal ions react with water to produce an acidic solution Mixtures of two acids or two bases with different pKa or pKb values Kb Ka solution is basic Kb Ka solution is acidic Kb Ka solution is nearly neutral
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