1.

Although thermodynamically feasible, in practice magnesium metal is not used for the reductionof alumina in the metallurgy of aluminium. Why ?

Answer»

Solution :Inspection of Ellingham diagram shows that `DeltaG` vs T curves for `Al_2O_3 and MgO` intersect at a point corresponding to very high temperaureof the order of 2000 K. This means above this temperature, `DeltaG` for the reaction :
`Al_2 O_3 + 3MG to 2AL + 3MgO`
would BECOME negative and hence reduction will be feasible. However, this temperautre is very high so that the process is uneconomical and technolgically DIFFICULT.


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