23 Titrations - What determines the displacement of one...

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1 3 Titration of Bases with a Strong Acid 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.00 14.00 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 55.0 60.0 65.0 70.0 75.0 mL HCl added pH NaOH Ephedrine Why are the curves different here, and the same here? Why is there an abrupt change in the pH at 37.5 mL? What determines the displacement of one curve from the other? Why is the pH 5.4 at the end point and not 7.0? How is an indicator chosen? 4 Review of weak acids, weak bases, their salts, and equilibrium situations. Why is ephedrine a base? Functional groups Amine Alcohol Aromatic ring – benzene ring Alkyl chain Behaves like ammonia, NH 3 . NH 3 + H 2 O NH 4 + + OH -
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2 5 Weak Bases & Reactions with a Strong Acid. Amines like ammonia and ephedrine. React with a strong acid NH 3 + HCl NH 4 Cl Producing a salt (ammonium chloride) that dissociates in water: NH 4 Cl NH 4 + (aq) + Cl - (aq) Thereby producing the conjugate weak acid E + HCl EHCl (a salt, ephedrine hydrochloride) EHCl EH + (aq) + Cl - (aq) 6 Anions of weak acids like formate and cyanide also are weak bases. HCOO - and CN - HCOOH and HCN (formic acid & hydrocyanic acid) They react with a strong acid HCOO - + HCl HCOOH + Cl - Thereby producing the conjugate weak acid CN - + HCl HCN + Cl -
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3 7 Weak bases and acids react with water Amines and their conjugate acids NH 3 + H 2 O NH 4 + + OH - , K b NH 4 + + H 2 O NH 3 + H 3 O + , K a Anions of weak acids and their conjugate acids. HCOO - + H 2 O HCOOH + OH - , K b HCOOH + H 2 O HCOO - + H 3 O + , K a CN - + H 2 O HCN + OH - , K b HCN + H 2 0 CN - + H 3 O + , K a 8 A) Initially B) In the middle C) At the equivalence point aka stoichiometric point D) Past the equivalence point
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23 Titrations - What determines the displacement of one...

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