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Lecture 19 10/17/05
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Principal species
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CasePrincipal species pH < pK a1 H2AH2A pK a1 < pH < pK a2 HA - pH > pK a2 A-A-
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Fractional composition
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p. 217
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Desired pH vs. pK How many mL of 0.8 M KOH should be added to 0.0375 moles oxalic acid (FW 90.35 g/mol) to give a pH of 4.40 when diluted to 500 mL. pK a1 = 1.252H 2 Ox HOx - + H + pK a2 = 4.266HOx - Ox -2 + H +
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Triprotic Acids H 3 A: Treat as monoprotic acid H2A-:H2A-: HA 2- : A 3- : Treat as monobasic
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Isoionic point pH when HA (neutral zwitterion) is dissolved in water
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Isoelectric point
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