Engineering
Chemistry
Extraction of Iron and Copper
Ellingham Diagram
Roasting Calcination or Smelting
Question
From the Ellingham diagram, identify the oxide which is reduced by the carbon at highest temperature among the following oxides.
MgO, CaO, TiO2 and Al2Ol3
MgO, CaO, TiO2 and Al2Ol3
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Solution
The Ellingham diagram plots the Gibbs free energy change (ΔG) for metal oxide formation vs temperature. Carbon reduction occurs when the carbon oxidation line (C → CO) intersects the metal oxide line. The oxide with the highest intersection temperature requires the most heat to be reduced by carbon.
From the diagram, the order of intersection temperatures is: Al2O3 > TiO2 > MgO > CaO.
Therefore, Al2O3 is reduced at the highest temperature.
Final Answer: Al2O3