CHEM 1120 1st Edition Lecture 13 Outline of Last Lecture I Acid Base Reactions a Autoionization of water b pH equation c Acid disassociation constant II Strong Acids and Bases a Strong acids b Strong bases c Weak acids Outline of Current Lecture I Equilibrium calculations a Percent ionization b Stepwise method II Weak bases and their relation to weak acids a Kb conjugate acid OH base b Categories of weak bases III Relationship between Ka and Kb a Kw Ka x Kb IV Acid Base properties of Salt solutions V Acid Base behavior and chemical structure a 3 factors Current Lecture I Equilibrium calculations a K x 2 concentration x b Percent ionization HX dissociated HX initial x 100 These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute II III IV V c For weak acids i High H concentrations ii Lower percent ionizations d Stepwise method suitable when Ka1 Ka2 Weak bases and their relation to weak acids a Strong bases are strong electrolytes b Weak bases are weak electrolytes c Base water conjugate acid OHd Kb conjugate acid OH base i Water is omitted ii Smaller Kb weaker base iii For all strong bases Kb 1 e 2 categories of weak bases i Neutral molecules with lone pairs of electrons ii Conjugate bases of weak acids Charged Relationship between Ka and Kb a Ka H X HX b Kb HX OH X c Ka x Kb Kw d Kw at 25 degrees C 1x10 14 e Pkw pKa pKb 14 Acid base properties of salt solutions a Often speak of Acids bases and salts suggesting that salts are neutral Not true b Acidic salts have NH4 ammonium c Basic salts NaCN KF d Neutral salts NaBr KCl e How do we predict Decide if and how its ions react with water f Conjugate base of a strong acid and cation of a strong base will not hydrolyze g Conjugate base of a weak acid and conjugate acid of a weak base will hydrolyze h What happens if both parents of a salt are weak Look at Kb and Ka Acid base behavior and chemical structure a Predicting acid strength is not easy b 3 major factors i H X bond polarity More positive H a more acidic H ii H X bond strength weaker H X bond a more acidic H iii Conjugate base stability more stable X more acidic H c Trends i Down and right stronger acids ii Up and left stronger bases d Compare conjugate acids e Factors affecting acid strength i In oxyacids in which an OH is bonded to another atom the more electronegative the atom is the more acidic the acid
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