The Synthesis and Analysis of Ammine Complexes of Copper and Silver Sulfate: An Undergraduate Laboratory Project

Abstract

An undergraduate chemistry laboratory project involving the synthesis of [Ag(NH3)2]2SO4 and Cu(NH3)4SO4 from the simple sulfate salts is described. Characterization of the stoichiometry of the complexes is accomplished by gravimetric and volumetric analysis. Silver is precipitated as the chloride and copper is precipitated as the hydroxide and converted to the oxide before weighing. The ammonia content of each complex is determined with a back titration using dilute nitric acid and sodium hydroxide. Typical student work gives results for the stoichiometry of the complexes within 1-5% of the theoretical values. The project provides a convenient preparation of two compounds whose identity and formula will not be obvious to the student. The analytical procedures illustrate the fundamentals of gravimetric and volumetric analysis and some basic characteristics of simple coordination complexes. The analytical data allow the student to determine the identity of each product by determining its empirical formula.