$Fe$ and FeO are in equilibrium with gas mixture of

composition $71\mathrm{.}8\%CO-28\mathrm{.}2\%C{O}_2$ at $1273K.$ Which of the

two solid phases disappears if the composition of the gas is

held constant and temperature of the system is increased?

$Fe(s)+\frac{1}{2}{O}_2(g)=$FeO$(s)G^o=-263700+64\mathrm{.}35T$

$C(s)+O_2(g)=C{O}_2(g),G=-394100-0\mathrm{.}84T$

$C(s)+\frac{1}{2}{O}_2(g)=CO,G^o=-111700-87\mathrm{.}65T$