Question

Which of the following reactions is an example of autoreduction?
(a) Fe₃O₄ + 4CO → 3Fe + 4CO₂
(b) Cu₂O + C → 2Cu + CO
(c) Cu²⁺ (aq) + Fe(s) → Cu (s) + Fe²⁺ (aq)
(d) Cu₂O + 1/2 Cu₂S → 3Cu + 1/2 SO₂

Answer 1

Explanation:

Which of the following reactions is an example of autoreduction?

(a) Fe₃O₄ + 4CO → 3Fe + 4CO₂

(b) Cu₂O + C → 2Cu + CO

(c) Cu²⁺ (aq) + Fe(s) → Cu (s) + Fe²⁺ (aq)

(d) Cu₂O + 1/2 Cu₂S → 3Cu + 1/2 SO₂

Answer 2

The following reaction is an example of autoreduction

(d) Cu₂O + 1/2 Cu₂S → 3Cu + 1/2 SO₂

Auto reduction is a process in metallurgy where the sulphide ores of metals like Cu, Pb, etc. are heated in the presence of Oxygen (in air) so that the sulphide is converted to oxide and then the remaining ore reacts in the absence of air to give off  SO₂ gas along with the metal itself.

In the fourth option, we see the sulphide ore of copper is autoreduced and  SO₂ and Cu are produced.

Cu₂O + 1/2 Cu₂S → 3Cu + 1/2 SO₂

So, (d) is the correct option.