Title

A 3-D Visualization of pH Titrations: Equivalence Point Cliffs, Dilution Ramps and Buffer Plateaus

Presenter Information

Daniel Barry

Presentation Type

Poster

Abstract

Acid/base chemistry is one of the most fundamental types of chemical reactions. 3-D surfaces have been generated to visualize how pH behaves during titration and dilution procedures. The surfaces are constructed by plotting computed pH values above a composition grid that has volume of base added in one direction and overall system dilution on the other. What emerge are surficial features that correspond to acid/base behavior in aqueous solutions. Equivalence point breaks become cliffs that pinch out with dilution. Buffer effects become plateaus. Dilution alone generates 45o ramps. A nice result of this visualization technique is that the limitations of the simplified Henderson-Hasselbalch equation can be seen by noting the conditions over which a plateau remains relatively flat. Because dissociation is driven by dilution, the surfaces can demonstrate when the solution of a weak acid becomes indistinguishable from that of a strong acid. Surfaces are presented for hydrochloric acid, HCl (a strong acid); acetic acid, CH3COOH (a weak monoprotic acid); oxalic acid, HOOCCOOH (a weak diprotic acid) and L-histidine hydrochloride, C6H9N3O2 . HCl (a weak triprotic acid).

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Apr 12th, 3:00 PM Apr 12th, 4:00 PM

A 3-D Visualization of pH Titrations: Equivalence Point Cliffs, Dilution Ramps and Buffer Plateaus

UC Ballroom

Acid/base chemistry is one of the most fundamental types of chemical reactions. 3-D surfaces have been generated to visualize how pH behaves during titration and dilution procedures. The surfaces are constructed by plotting computed pH values above a composition grid that has volume of base added in one direction and overall system dilution on the other. What emerge are surficial features that correspond to acid/base behavior in aqueous solutions. Equivalence point breaks become cliffs that pinch out with dilution. Buffer effects become plateaus. Dilution alone generates 45o ramps. A nice result of this visualization technique is that the limitations of the simplified Henderson-Hasselbalch equation can be seen by noting the conditions over which a plateau remains relatively flat. Because dissociation is driven by dilution, the surfaces can demonstrate when the solution of a weak acid becomes indistinguishable from that of a strong acid. Surfaces are presented for hydrochloric acid, HCl (a strong acid); acetic acid, CH3COOH (a weak monoprotic acid); oxalic acid, HOOCCOOH (a weak diprotic acid) and L-histidine hydrochloride, C6H9N3O2 . HCl (a weak triprotic acid).