These equilibria can be discussed in terms of thermodynamic functions.
For the reaction :
(i) M(s)+12O2(g)→MO(s)
(ii) 12C(s)+12O2(g)→12CO2(g)
(iii) C(s)+12O2(g)→CO(g)
(iii) CO(g)+12O2(g)→CO2(g)
The temperature dependence of
Δ˚G of reaction (i) to (iv) is shown in the given diagram. This is known as the Ellingham diagram. With the help of the Ellingham diagram, one can easily predict the most suitable reducing agent for the reduction of metal oxides.
AI2O3 can be reduced by carbon at a temperature of: