Question

Name the metal oxides which can be reduced by carbon monoxide among the following metals
Ca Fe Mg K

Answer 1

The unit Hydrogen in the Reactivity Seriesshowed where hydrogen fits into the 

Reactivity Series and how it is used to extract tungsten metal. But another non-metal, carbon, is even more important in extraction processes. Look at the position of carbon in the Reactivity Series:

Metals are often found in their ores as oxides or sulfides. The sulfides, such as lead sulfide, can be converted to the oxide by roasting in air:

lead sulfide  +  oxygen    lead oxide  +  sulfur dioxide
2 PbS(s)  +  3 O2(g)    2 PbO(s)  +  2 SO2(g)

Then carbon can be used to extract any of the metals below it in the Reactivity Series. It is mixed and heated with the oxide to displace the metal.
Here is the equation for the reaction of lead oxide and carbon:

lead oxide  +  carbon    lead  +  carbon dioxide
2 PbO(l)  +  C(s)    2 Pb(s)  +  CO2(g)