Choose the correct option of temperature at which carbon reduced `FeO` to iron and produces `CO`

Options

A. Below temperature at point A
B. Approximately at the temperature corresponding to point A
C. Above temperature at point A but below temperature at point D
D. Above temperature at point A

Answer

D

Explanation

The changes in Gibbs energy that occur when one mole of oxygen is used plotted against temperature for a number of reactions of metals to form their oxides. Such a graph is called an Ellingham diagram for oxides.
(i) The graph for metal oxide all slope upwards because the change in Gibbs energy becomes less negative with increase in temperature.
(ii) Each plot follows a straight line unless there is some change in phase.
(iii) For most metals, when the temperature is increased, a point will be reached when the line crosses ` Delta G = 0` line. Below this temperature `Delta_(f)G^(0)` of the oxide is negative and hence the oxide is stable. Above this temperature it is positive and hence the oxide becomes unstable and decomposes on its own into metal and oxygen.
In the figure shown , the temperature above point A :
`Delta_(f)G_("(C,CO)")^(0) lt Delta_(f)G_("(Fe,FeO)")^(0)` or value of `Delta_(f)G_("(C,CO)")^(0)` is more negative.