Synthesis and Chemistry
Salts of the peroxodisulfate ion are relatively stable but in acidic solution they react to give hydrogen peroxide, H2O2: O3S-O-O-SO32- + 2H+ ? HO3S-O-O-SO3H HO3S-O-O-SO3H + H2O ? HO3-O-OH + H2SO4 HO3-O-OH + H2O ? H2O2 Reaction (3) in Table (1) showed no signs of change in the solution upon adding K2S2O8 it can be assumed that the peroxodisulfate ion had been converted to H2O2. CONCLUSION In this experiment, K2S2O8 was synthesized via electrolysis of the aqueous solution of H2SO4 and K2SO4. Using Faraday’s equation, the expected yield was 8. 432 g but only 12% (1.045 g) of this yield was recovered. This can be due to the fact that ideal conditions for maximum yield of K2S2O8 was not maintained (overvoltage, low temperature of solution, etc. ) increasing the oxidation of H2O leading to the production of more O2 gas. The peroxodisulfate anion is also known to be a strong oxidizing agent, even stronger than H2O2 thus comparative tests were done to confirm this. Peroxodisulfate anion also has the ability to serve as a counterion for precipitation by preparing copper (II) complex.
An IR spectrum for the product was obtained and sharp peaks at 1297. 61 cm-1 was observed, noting the presence of a C-C bond in the product which can be seen in pyridine’s molecular structure. Sharp peaks at 1047. 24cm-1 and 1069. 29cm-1 were evident accounting for the S=O in the peroxodisulfate anion. Qualitative tests are recommended to confirm the presence of the Cu2+ ion in the collected product. Its capability to be counterion, together with its strong oxidizing property, peroxodisulfate anion allowed for stabilization of the unusual oxidation state of 2+ for silver which was observed by preparing an analogous silver (II) complex.
The IR spectrum for the collected product showed the prominent peaks for the S=O from the peroxodisulfate ion (1042. 82cm-1 and1059. 27cm-1) and peaks for the C-C (1303. 61cm-1) and C-H (3028. 39cm-1 and 3097. 87cm-1) from the pyridine. A test for the presence of the silver (II) complex is recommended to confirm the presence and success of this synthesis. Overall, the synthesis for K2S2O8 was a success. Though further investigation is recommended for the distinct properties of the perocodisulfate ion. 3 REFERENCES 1. Girolmi, G. S. ; Rauchfuss, T. B. ; Angelici, R. J. Synthesis and Technique in Inorganic Chemistry: A Laboratory Manual.
University Science Books, 1999. 2. Miller, F. ; Wilkins, C. Infrared Spectra and Characteristic Frequencies of Inorganic Ions. Ph. D. Dissertation, Mellon Institute, Pittsburgh, PA, 1952. 3. Szafran, Z. ; Pike, R. M. ; Singh, M. M. Microscale Inorganic Chemistry – A Comprehensive Laboratory Experience. Wiley, 1991. 4. Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coordination Compounds, Parts A and B. Wiley, 1997. 5. University of Calgary, Department of Chemistry, Chemistry 331, Inorganic Chemistry: Main Group Elements, Online Lab Manual, Fall 2013, Project #2 pp 33-36.