The solubility of magnetite and hydrolysis of ferrous ion in aqueous solutions at elevated temperatures
| Autor: | F. H. Sweeton, C.F Baes |
|---|---|
| Rok vydání: | 1970 |
| Předmět: |
Molality
Aqueous solution Hydrogen Inorganic chemistry Analytical chemistry chemistry.chemical_element Atomic and Molecular Physics and Optics Ferrous chemistry.chemical_compound chemistry General Materials Science Qualitative inorganic analysis Physical and Theoretical Chemistry Solubility Equilibrium constant Magnetite |
| Zdroj: | The Journal of Chemical Thermodynamics. 2:479-500 |
| ISSN: | 0021-9614 |
| DOI: | 10.1016/0021-9614(70)90098-4 |
| Popis: | The solubility of magnetite (Fe3O4) in dilute aqueous solutions saturated with H2 at 1 atm at 25 °C has been measured at temperatures between 50 and 300 °C. The solutions have ranged from KOH of molality 400 × 10−6 mol kg−1 to HCl of molality 100 × 10−6 mol kg−1. The measurements were made by the continuous flow of solution over a bed of specially prepared pure magnetite. It was found that, under these conditions of temperature and hydrogen activity, Fe3O4 does not transform to HFe5O8 or γ-Fe2O3. The results have been fitted with a scheme of soluble species consisting of Fe2+, FeOH+, Fe(OH)2, and Fe(OH)3−, and the equilibrium constants for the reactions ( 1 3 Fe 3 O 4 + (2−b)H + + 1 3 H 2 (g) = Fe(OH) (2−b)+ b + 4 3 H 2 O have been calculated. The temperature coefficients of the constants for Fe2+ and FeOH+ were found to be negative, and those of Fe(OH)2 and Fe(OH)3−, positive. The estimated values of ΔHo and ΔSo for these reactions are also given. The value of log10(K/mol kg−1) at 25 °C for the reaction Fe 2+ + H 2 O = FeOH + + H + , has been determined by extrapolation of the solubilities and has been found to be (−9.3 ± 0.5). The solubilities have been combined with other thermodynamic data to calculate ΔGo, ΔHo, and ΔSo for the formation of Fe2+ and FeOH+ by the reaction: Fe + bH 2 O + (2−b) H + = Fe(OH) (2−b)+ b + H 2 (g) . The extrapolated value of ΔGo for the formation of Fe2+ at 25 °C by this reaction gives an Eo of (0.475 ± 0.010) V. |
| Databáze: | OpenAIRE |
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