Gibbs Free Energy of Formation of Synthetic Cryptomelane
Cryptomelane with a formal composition of K0.88Mn(III)0.24Mn(IV)7.60O16.00∙0.33H2O was precipitated from a solution of sulfuric acid containing dissolved manganese sulfate. The oxidation state of manganese in solution was controlled by bubbling pure oxygen gas through and the pH was raised from 1.0...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | deu |
| Published: |
Swiss Chemical Society
1984-12-01
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| Series: | CHIMIA |
| Online Access: | https://www.chimia.ch/chimia/article/view/9630 |
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| Summary: | Cryptomelane with a formal composition of K0.88Mn(III)0.24Mn(IV)7.60O16.00∙0.33H2O was precipitated from a solution of sulfuric acid containing dissolved manganese sulfate. The oxidation state of manganese in solution was controlled by bubbling pure oxygen gas through and the pH was raised from 1.00 to 2.90 by addition of KOH.
Measurements of pH and Eh as well as determination of ion activities in equilibrium with the obtained solid led to a pH = f(Eh) curve with an inclination corresponding to the synthesis equation:
(0.88K+) + 7.84Mn2+ + 16.01H2O ⇌ K0.88Mn(III)0.24Mn(IV)7.60O16.00∙0.33H2O + 31.36H+ + 15.68e
By Nernst’s equation an E° value was determined permitting the calculation of Gibbs free energy of reaction, (ΔGR)°298 = 1323.98 ± 3.29 kJ∙mol-1 and formation, ΔG°fCRYP = - 4482.08 ±3.40 kJ∙mol-1 of synthesized cryptomelane.
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| ISSN: | 0009-4293 2673-2424 |