$\stackrel{0}{\mathrm{Fe}}+\mathrm{CuSO}_{4} \rightarrow \stackrel{+2}{\mathrm{FeSO}_{4}}+\mathrm{Cu}$
$\stackrel{0}{\mathrm{Fe}}+5 \mathrm{CO} \rightarrow \stackrel{0}{\mathrm{Fe}}(\mathrm{CO})_{5}$
$\stackrel{0}{Fe}+\mathrm{H}_{2} \mathrm{O} \rightarrow \stackrel{+3}{\mathrm{Fe}_{2} \mathrm{O}_{3}}+\mathrm{H}_{2}$
above reactions shows the oxdiation state of iron for all given condition.