Ellingham diagrams were 1st constructed by Harold Ellingham in 1944. (image will be updated soon)
Following are the Salient Features of it –
It is a plot of ∆G°in kJ/mol of oxygen and temperature of formation of oxide.
As ∆G° becomes less negative at high temperatures so each line of converting metals into metal oxide slope upwards.
Each plot line is straight line except some lines where the change in phase such as solid 🡪 liquid or Liquid 🡪 Gas etc. takes place.
With increase in temperature slope lines cross ∆G°= 0 which means for them ∆G°>0. Theoretically this happens in case of mercury, silver and gold.
Few applications of Ellingham diagram are listed below –
It is used to evaluate the ease of reduction of metal oxides and sulfides.
In metallurgy it is used to predict the equilibrium temperature between metal, oxide and oxygen. It also predicts the reaction of metals with nitrogen, sulfur and nonmetals.
By Ellingham diagram we can predict the condition under which an ore can be reduced to its metal.
It is used for finding the best suitable reducing agent for reduction of metal oxides.
It is used to find out the feasibility of thermal reduction of an ore.
As we know, the Ellingham curve for aluminium lies below most metals such as Fe, Cr etc. which indicates that Al can be used as the reducing agent for oxides of all these metals.
It has few limitations as well which are listed below –
It ignores the reaction kinetics means it does not provide any information about kinetics of the reduction reaction.
The analysis is thermodynamic in nature, it means the reactions which are predicted by the Ellingham diagram can be very slow.
It assumes that the reactants and products are in equilibrium, but it is not always the case.
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