Question

Choose the correct option of temperature at which carbon reduces \[\ce{FeO}\] to iron and produces \[\ce{CO}\].

Options

• Below temperature at point A.

• Approximately at the temperature corresponding to point A.

• Above temperature at point A but below temperature at point D.

• Above temperature at point A.

Answer 1

Above temperature at point A.

Explanation:

\[\ce{FeO + C -> Fe + CO}\]

It can be seen as a couple of two simpler reactions:

\[\ce{FeO -> Fe + 1/2 O2 (ΔG^Θ_{FeO, Fe})}\]

\[\ce{C + 1/2 O2 -> CO (ΔG^Θ_{C, CO})}\]

Total Gibb's energy change becomes

\[\ce{ΔG^Θ_{(C, CO)} + ΔG^Θ_{(FeO, Fe)} ΔrG^Θ}\]

In \[\ce{ΔG^Θ}\] verus T plot, the plot Fe to FeO goes upward and the plot for C to CO goes downwards.

At temperature above point A, the C to CO line comes below Fe to FeO and \[\ce{ΔG^Θ_{(C, CO)} < {ΔG^Θ_{(Fe, FeO)}}}\]

So on this range, \[\ce{C}\] will reduce \[\ce{FeO}\] to \[\ce{Fe}\] and itself be oxidized to \[\ce{CO}\].