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Preparation of chromium metal

Ellingham chrome

From chromium oxide.

 

Cr2O3 + 2Al ->2Cr +Al2O3

Shortly after the isolation of the aluminium was discovered that the mixture of this with certain metal oxides allows reducing them to the metallic state. This reaction, known as aluminotermia, is also a large amount of heat and light. In fact, the heat produced is used to speed up the process. After the reaction, the metal may be collected in the form of bright blood cells, the temperature reached is sufficient to melt the metal.

The thermodynamic justification of this reaction is usually done through the Ellingham diagram. He represents the free energy of formation of different oxides versus temperature. Thus oxides located at the top of the diagram (with less negative free energy) may be reduced by the metals from the bottom of the diagram (whose oxides have more negative energies of formation and therefore whose formation is thermodynamically most favoured). For example, the training of Cr2O3 from to the (blue line, at the bottom) is more favored than the formation of Al2O3 from Al (green line, in the middle), so it is possible to reduce Cr2O3 to Cr with to the. The difference in energy is released in the form of heat and light.

 

Reproducir

chrome


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