Question

Given Below are the steps for extraction of copper from its ore. The balanced reaction involved in reduction of copper(I) oxide with copper(I) sulphide is given in the reaction below.
\[\text{2C}{{\text{u}}_{\text{2}}}\text{O+C}{{\text{u}}_{\text{2}}}\text{S}\xrightarrow{\text{ }\!\!\Delta\!\!\text{ }}\text{6Cu+S}{{\text{O}}_{\text{2}}}\]
This reaction is known as:
(a) Auto-reduction
(b) Catalytic-reduction
(c) Acid reduction
(d) None of these

Answer 1

Hint: Solve this question by first understanding what ‘reduction’ means. A compound is said to be reduced when it gains an electron or proton in a chemical reaction. The terms ‘auto’, ‘catalytic’ and ‘acid’ refer to the cause of reduction.

Complete step by step answer:
Let us take a look at the reaction first. This reaction is involved in extraction of copper from its ore. As we can see, when copper(I) oxide and copper(I) sulphide is heated, it produces pure copper. This ‘pure’ copper is also known as ‘blister’ copper.
Also, as there is no catalyst or acid involved in the reaction, this reaction is neither catalytic-reduction nor acid reduction.
Since no copper gets reduced without any external agent, this reaction is an example of auto-reduction.
The extraction of copper from its ore actually occurs in two steps –
(i) Partial roasting of its sulphide ore
\[\text{2C}{{\text{u}}_{\text{2}}}\text{S+3}{{\text{O}}_{\text{2}}}\to \text{2C}{{\text{u}}_{\text{2}}}\text{O+2S}{{\text{O}}_{\text{2}}}\]
(ii) Heating after stopping oxygen supply
\[\text{2C}{{\text{u}}_{\text{2}}}\text{O+C}{{\text{u}}_{\text{2}}}\text{S}\xrightarrow{\text{ }\!\!\Delta\!\!\text{ }}\text{6Cu+S}{{\text{O}}_{\text{2}}}\]
Therefore, the answer is – option (b) – The given reaction is an example of auto-reduction.

Additional Information:
Copper(I) oxide is a red coloured solid component and is one of the main ores of copper.

Note: Auto-reduction is also known as air-reduction and is a popular method in metallurgy, used for extraction of metals. This method is generally used for less electropositive metals, like Copper, Lead and Mercury.