Question

A metal obtained by auto reduction or self reduction _____.
A. Na
B. Zn
C. Fe
D. Cu

Answer 1

Hint- In order to deal with this question first we will define the term reduction then we will proceed further by using the principle ore for the following options. We will check for the process where no external reducing agent is used making it a self reduction.

Complete answer:
Reduction is a part of mining of metal from the ore.
Reduction reaction does not undergo itself, rather it happens with oxidation of another species. So it is a part of the redox reaction.
Copper pyrite is the principal source of copper and copper is mined from the mine. During this process no external reducing agent is used so it is an example of self reduction.
Self-reduction happens in Bessemer converter reaction as
$
  2FeS + 3{O_2} \to 2FeO + 2S{O_2} \\
  C{u_2}O + FeS + C{u_2}S + FeO \\
  FeO + Si{O_2} \to FeSi{O_3}{\text{ }}({\text{removed as slag}}) \\
  C{u_2}S + 3{O_2} \to C{u_2}O + S{O_2} \\
 $
Self reduction:
$C{u_2}S + 2C{u_2}O \to 6Cu + S{O_2}$
Hence, self-reduction takes place in the case of Copper.

So, the correct answer is option D.

Note- Redox is a kind of chemical reaction in which atomic oxidation states are altered. Redox reactions are characterized by real or structured electrons transfer between chemical species, most commonly with one species undergoing oxidation while another species is undergoing reduction. Most copper is used in electrical devices such as cabling and engines. That's because it conducts very well both heat and electricity, and can be drawn into wires. This also has building applications ( e.g. roofing and plumbing), and commercial equipment ( e.g. heat exchangers).