Test: Metallurgy - Class 10 MCQ

Reduction of an oxide by a substance depends on reducing ability of the substance. As Carbon(C) is more reductive than chromium oxide(Cr₂O₃), it has more affinity towards oxygen. Therefore, zinc oxide can reduced to metal by heating with carbon but not chromium oxide.

The oxides of potassium is of highly reactive metalware very stable and cannot be reduced by the most common reducing agent like carbon to obtain free metals. this is because these metals have more affinity for oxygen than carbon. so carbon is unable to remove oxygen from these metals. during electrolysis, the negatively charged electrode acts as a powerful reducing agent by supplying electrons to reduce the metal ions into metal.

Metals that are low in the activity series are very un-reactive. The oxides of these metals can be reduced to metals by heating alone. For example, mercury is obtained from its ore, cinnabar (HgS), by the process of heating.