Photochemistry - (filter paper on which the reagents had...

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Analysis: Photochemistry is an interesting branch of chemistry that utilizes the photochemical excitation of molecules to create a strong color in the presence of ultraviolet radiation. The experiment used oxalic acid as the main source of oxalate ion that is being generated when oxalic acid losses two protons from its stable oxidation state. Interaction of lights with this anion leads to its oxidation and releases carbon dioxide and an electron which then reduces the Fe(III) ion to Fe(II) ion. The redox chemistry is readily apparent in the reduction of Oxalate: C 2 O 42- + hv 2 CO 2 + 2 e - Fe 3+ + 1 e- Fe 2+ Overall reaction: 2 Fe 3+ + C 2 O 4 2- + hv 2 Fe 2+ + 2 CO 2 The Fe(II) formed in the overall reaction combines with CN- preset in the solution due to Potassium Ferricyanide to form the complex [Fe(CN) 6 ] 4-, which in turn gives the insoluble Prussian blue, Fe(III) 4 [Fe(CN) 6 ] 3, adhering to the fibers of the cloth or paper
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Unformatted text preview: (filter paper) on which the reagents had been coated. Fe 2+ + 6 CN- [Fe(CN) 6 ] 4-3 [Fe(CN) 6 ] 4-+ 4 Fe 3+ Fe(III) 4 [Fe(CN )6 ] 3 The blue color results from interaction between the two irons in different oxidation states (Fe(II) and Fe(III)). Conclusion: In general, the redox reaction provides the appearance of the Prussian blue color in the filter paper due to the interaction between the two Fe ions present existing in different oxidation states. The oxalate ion is in general, the main source of protons that give rise to the reduction of Fe(III) to Fe(II). Furthermore the Fe(II) formed will react with the cyanide ion provided by the Potassium Ferricyanide in the solution to form the complex [Fe(CN) 6 ] 4-, which is the one responsible for the Prussian Blue color adhering on the filter paper....
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