What is 'Ellingham diagram' ? Write any two points of its significance .

Explanation

More negative the value of `Delta G`, the greater is the tendency of the element to combine with oxygen. These results can be plotted as a graph. Such plots of `Delta G` against T (in Kelvin ) are called the Ellingham diagrams.
Significance :
(i) The positive slope of metal oxides shows that their stabilities increase with increase in temperature. The decrease in their stability is due to an increase in `Delta G` value.
The sudden change in the graph shows a phase change that is, change from solid to liquid or from liquid to vapour.