This paper describes a first-year
undergraduate exercise involving
the synthesis of an “unknown” polyiodide salt, (NMe4)[I5], and the determination of its formula using
the classic iodine–thiosulfate (iodometric) titration. The
exercise introduces students to simple synthetic and titrimetric techniques,
assists the development of their chemical and glassware handling and
titrimetric skills, and acquaints them with unfamiliar polyiodide
compounds. It also introduces
students to key chemical concepts such as The Law of Definite Proportions,
percentage elemental composition, empirical chemical formulas, quantitative
stoichiometric reactions, and halogen catenation.
This paper describes an upper-division
undergraduate exercise involving
the synthesis and iodometric and infrared spectroscopic analysis of
the peroxide double salt [Zn(NH3)4][Mo(O2)4]. Here, iodometric methods are employed to determine
the peroxide content of the compound, a procedure widely used for
the industrial analysis of peroxides. The exercise increases student
proficiency in synthesis, the handling of reactive chemicals, and
titrimetry, while introducing aspects of metal peroxide chemistry
and key chemical concepts related to high-coordination number complexes,
kinetic versus thermodynamic stability, and group theoretical treatments
of vibration spectroscopy.
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