Spatial Heterogeneity and Imperfect Mixing in Chemical Reactions: Visualization of Density-Driven Pattern Formation
| Autor: | Harold M. Hastings, Sabrina G. Sobel, Matthew Testa |
|---|---|
| Rok vydání: | 2009 |
| Předmět: |
010304 chemical physics
Chemistry Stereochemistry lcsh:QD450-801 Pattern formation lcsh:Physical and theoretical chemistry Model system Chemical reactor 010402 general chemistry 01 natural sciences Chemical reaction 0104 chemical sciences Spatial heterogeneity lcsh:Chemistry lcsh:QD1-999 Chemical physics 0103 physical sciences lcsh:Q Imperfect Physical and Theoretical Chemistry lcsh:Science Mixing (physics) |
| Zdroj: | Research Letters in Physical Chemistry, Vol 2009 (2009) |
| ISSN: | 1687-6881 1687-6873 |
| DOI: | 10.1155/2009/350424 |
| Popis: | Imperfect mixing is a concern in industrial processes, everyday processes (mixing paint, bread machines), and in understanding salt water-fresh water mixing in ecosystems. The effects of imperfect mixing become evident in the unstirred ferroin-catalyzed Belousov-Zhabotinsky reaction, the prototype for chemical pattern formation. Over time, waves of oxidation (high ferriin concentration, blue) propagate into a background of low ferriin concentration (red); their structure reflects in part the history of mixing in the reaction vessel. However, it may be difficult to separate mixing effects from reaction effects. We describe a simpler model system for visualizing density-driven pattern formation in an essentially unmixed chemical system: the reaction of pale yellow Fe3+ with colorless SCN− to form the blood-red Fe(SCN)2+ complex ion in aqueous solution. Careful addition of one drop of Fe(NO3)3 to KSCN yields striped patterns after several minutes. The patterns appear reminiscent of Rayleigh-Taylor instabilities and convection rolls, arguing that pattern formation is caused by density-driven mixing. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|