Which metal oxide cannot be reduced by carbon?

Which metal is the least reactive?

During the refining of copper by electrolysis,copper deposits at the $....$.

Which metal does not react with cold or hot water,but reacts with steam to produce $H_2$ gas?

Write chemical equations for the reactions taking place when:
$(i)$ iron is strongly heated in air.
$(ii)$ lead carbonate is calcined.
$(iii)$ chromium oxide $(Cr_{2}O_{3})$ is heated with aluminium powder.

Which of the following metals exist in their native state in nature?
$(i)$ $Au$
$(ii)$ $Cu$
$(iii)$ $Ag$
$(iv)$ $Fe$