Association for Biology Laboratory Education

Teaching Buffering by Showing Its Effects
 

Robert J. Kosinski & C. Kaighn Morlok

Tested Studies in Laboratory Teaching, 2011, Volume 32

Abstract

In this laboratory, students identify “mystery” solutions as either distilled water, monobasic phosphate only, dibasic phosphate only, or combined phosphate buffer. The solutions are titrated with both acid and base, and the increase of hydrogen or hydroxide ions (not pH) is plotted against mL of acid of base added. These plots make the identification of the “mystery” solutions obvious. Solutions without buffering against acid (for example) show a linear increase in hydrogen concentration when titrated with acid. Solutions with buffering against acid show nearly no increase until the buffering is exhausted, and then the hydrogen ion concentration increases dramatically.

Keywords:  phosphate, buffer, titration

Dalhousie University (2010)