Chemistry 1027A/B Lecture Notes - Lecture 9: Coordinate Covalent Bond, Lewis Acids And Bases, Conjugate Acid
15 Mar 2015
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Weak acids and bases only partially ionize. Acid produces h+ (h3o+) ions in water. Lewis acid: accept a pair of electrons from another atom, formation of coordinate covalent bond, ex. Lewis base: donates pair of electron to another atom, formation of an acid-base adduct, ex. Weak acid: ha h+ + a, ka = [h+][a-]/[ha] Weak base: b + h2o = bh+ + oh, kb = [bh+][oh-]/[b] Larger the k value = greater ionization. Ka simplified: pka = -logka (pka becomes smaller as acid strength increases) Kb simplified: pkb = -logkb (pkb becomes smaller as base strength increases) Percent ionization < 5% - approximation is valid. C/ka: result greater than 400 approximation is valid. Species produced by ionization of weak acid. Behaves like a weak base in solution. Species produced by ionization of weak base. Behaves like a weak acid in solution. Kw = ka x kb = [h3o + ][a. Stronger the weak acid the weaker the conjugate base.
