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Predict the conditions under which(а) Aluminium might be expected to reduce magnesia. (b) Magnesium could reduce alumina. |
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Answer» The conditions under which: (a) Ellingham diagram is used to predict thermodynamic feasibility of reduction of oxides of one metal by another metal. Any metal can reduce the oxides of other metals that are located above it in the Ellingham diagram. In the Ellingham diagram, for the formation of magnesia (magnesium oxide) occupy lower position than aluminium oxide. Therefore aluminium cannot be used to reduce the oxides of magnesium (magnesia). Above 1623K, A1 can reduce MgO to Mg, so that ArG° becomes negative and the process becomes thermodynamically feasible. 3MgO + 2Al + 1623 k ⟶ Al2O3 + 3 Mg (b) 1. \(\frac{4}{3}\)+ Al + O2 ⟶ \(\frac{2}{3}\)Al2O3 2. 2Mg + O2 ⟶ 2MgO At the point of intersection of the Al2O3 and MgO curves in Ellingham diagram. ∆G° becomes zero for the reaction. \(\frac{2}{3}\)+ Al2O3 + 2Mg ⟶ 2 MgO + \(\frac{4}{3}\)Al |
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