In this experiment, a sample of K2S2O8 was prepared by the electrolysis of an aqueous solution of H2SO4 and K2SO4. The peroxodisulfate anion, S2O82-, was also observed for its ability to serve as a counterion for precipitation by preparing a copper (II) complex by reacting hydrated copper (II) sulfate with ammonium peroxodisulfate in the presence of pyridine. This same ability, coupled with its strong oxidizing ability allowed for stabilization of the unusual oxidation state of 2+ for silver which was observed by preparing an analogous silver (II) complex by reacting silver (I) nitrate with ammonium peroxodisulfate in the presence of pyridine. IR spectra for the three products were The above amount of reagents yielded 0.965 g (68.02%) of [Cu(py)4]S2O8.
D. Preparation of Tetrapyridinesilver(II) Peroxodisulfate A solution of ammonium peroxodisulfate (0.514g in 15mL of water, 2.25E-3 mol) was prepared and to this solution, 1.5mL of pyridine was added slowly while stirring, followed by 3mL of silver nitrate solution (5% w/v, 8.83E-4 mol). The solution was cooled to below 10 °C and the orange solid formed was filtered, washed with 5mL of ice cold water, then twice with 5mL of alcohol. The above amount of reagents yielded 0.158 g (43.04%) of [Ag(py)4]S2O8.
RESULTS
Table 1 REACTIONS OF PEROXODISULFATE AND HYDROGEN PEROXIDE Reactions Peroxodisulfate Hydrogen Peroxide 1) Acidified KI solution, warming gently Pale yellow solution; colour turned dark orange after a few seconds; sustained a more reddish colour Solution turned deep red/brown; no precipitate 2) Silver nitrate solution Initially clear; turned charcoal gray after ~10 secs; sustained a black colour Clear solution, no change on addition of H2O2 3) MnSO4 solution in 2M H2SO4, containing 1 drop of AgNO3 solution Clear solution Clear solution, no change on addition of H2O2 4) Titanium (IV) sulphate solution White cloudy solution Solution turned reddish brown
Table 2.1 SPECTRAL DATA FOR COMMERCIAL K2S2O8 Peak (cm-1) Assignment 440.82 S-O bending 796.96 K-O stretching; slightly broad 1045.49 S=O stretching; broad and slightly
