Question

Which reducing agent is employed to get copper from the leached low grade copper ore?

Answer 1

Hint: Reducing agent, also known as a reducer or reductant, is an element or a compound which donates or loses an electron to an oxidizing agent or an electron recipient in a redox reaction. Good reducing agents generally possess small ionization energy as well as low electronegativity.

Complete answer
Copper can be obtained from the low-grade copper ore through the process of leaching utilising acid or bacteria (thus, the process is known as bioleaching). Leaching is considered to be an alternative method to copper mining. Leaching is actually a process in which metal ore is treated with a suitable reagent which dissolves metal ore only and the impurities are left behind. In this process of leaching, First of all, the metal ore (i.e. copper ore) is treated with the dilute sulphuric acid. You will see that this will slowly trickle down through the copper ore for a period of few months, and will dissolve copper leading to the formation of a weak solution of copper sulfate. The copper metal can be then recovered through the process of electrolysis.
Therefore, the solution consisting of copper can be reduced by the aid of reducing agents such as scrap iron or hydrogen to obtain copper metal. The reactions with reducing agents are mentioned below:
\[
  C{u^{2 + }}\left( {aq} \right) + Fe \to Cu\left( s \right) + F{e^{2 + }}\left( {aq} \right) \\
  C{u^{2 + }}\left( {aq} \right) + {H_2}\left( g \right) \to Cu\left( s \right) + 2{H^ + }\left( {aq} \right) \\
\]
Hence, the correct answer is scrap iron or hydrogen.

Note:
The main issue with the process of bioleaching in extracting copper from low grade copper ore is that it yields toxic substances, including sulphuric acid, which causes damage to the environment. However, bioleaching does not require high temperature.