1. Ellingham diagram help us in predicting the feasibility of thermal reduction of ore. The criteria is that at a given temperature Gibbs energy of reaction should be negative.
2. Below 1000 K CO is the good reducing agent while above 1000 K carbon is the good reducing agent. This is because below 1000 K the (CO,CO2) line is below the (Fe,FeO) line. But, above 1000 K the (C,CO2) line is below the (Fe,FeO) line.