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Weak Bases

Weak Bases. Many substances behave as weak bases in water React with water removing protons from the H 2 O thus forming OH - ions Weak Base + H 2 O  Conj. Acid + OH -. Ammonia. NH 3 + H 2 O  NH 4 + + OH - K b = [NH 4 + ][OH - ] [NH 3 ]

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Weak Bases

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  1. Weak Bases

  2. Many substances behave as weak bases in water • React with water removing protons from the H2O thus forming OH- ions • Weak Base + H2O  Conj. Acid + OH-

  3. Ammonia • NH3 + H2O  NH4+ + OH- • Kb = [NH4+][OH-] [NH3] • Kb – base-dissociation constant

  4. Example • Calculate the concentration of OH- in a .15M solution of NH3.

  5. Weak Bases • Ammonia NH3 Kb = 1.8 x 10-5 • Pyridine C5H5N Kb = 1.7 x 10-9 • Hydroxylamine H2NOH Kb = 1.1 x 10-8 • Methylamine NH2CH3 Kb = 4.4 x 10-4 • Nicotine C10H14N2 Kb = 7 x 10-7 • Hydrosulfide HS- Kb = 1.8 x 10-7 • Carbonate CO32- Kb = 1.8 x 10-4 • Hypochlorite ClO4- Kb = 3.3 x 10-7

  6. Example • Calculate the pH of .010M solution of sodium hypochlorite, NaClO.

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