Titration of a Solid Acid Monitored By X-Ray Diffraction

Abstract

The solid state is becoming an increasingly important topic in the general chemistry curriculum due to the cultural impact of materials science and technology. Herein we present a solid-state laboratory experience to enhance the traditional aqueous acid�base titration experiment in the first-year undergraduate honors chemistry course or more advanced course. a-zirconium phosphate is a solid acid that can easily be prepared. In a cooperative titration experiment, each student pair reacts fixed amounts of zirconium phosphate with increasing equivalents of NaOH(aq). Upon reaction with sodium hydroxide, the acidic proton within the crystalline lattice of zirconium phosphate is replaced by the sodium ion. The progress of the reaction can be monitored with a pH meter and then a powder X-ray diffractometer. From the X-ray diffraction patterns, students calculate the interplanar spacings before and after the reaction. The spacings increase until the molar equivalence point is reached, indicating incorporation of the sodium ion into the crystal