Essay on Synthesis and Chemistry of K2S2O8

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SYNTHESIS AND CHEMISTRY OF K2S2O8

ABSTRACT

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
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Thus, it is an important and popular tool for structural elucidation and compound identification.

EXPERIMENTAL METHOD

A. Preparation of potassium peroxodisulfate
A potential set-up was prepared wherein the 25 x 150 mm test tube was filled with K2SO4 (30mL, 0.15 mol) saturated at 0 °C in 5M H2SO4. The test tube was immersed in ice, power supply was adjusted to give the solution a current of ~3.0 amps. Current was read and recorded as accurately a possible, as well as the time over which electrolysis was carried out. K2S2O8 precipitated over a period of 45-50 minutes during which the temperature was maintained close to 0 °C (~8 °C or lower) during electrolysis.
Crystals were collected in a Buchner funnel, washed with alcohol, then ether, then transferred into a sample tube for storage.

B. Reactions of Peroxodisulfate Ion
A saturated solution of K2S2O8 in water was prepared and the following reactions were carried out. The results were compared with similar reactions using hydrogen peroxide.
1) Acidified KI solution, warming gently
2) Silver nitrate solution
3) MnSO4 solution in 2M H2SO4, containing 1 drop of AgNO3 solution
4) Titanium (IV) sulphate solution

C. Preparation of Tetrapyridinecopper(II) Peroxodisulfate
Solutions of CuSO45H2O (0.506 g in 10mL water, 3.17E-3 mol) and ammonium peroxodisulfate (1.030 g in 10mL water, 4.51E-3 mol) were prepared and mixed

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