Consider the following redox reaction: 2Cu2O (s) + Cu2S (s) —

Consider the following redox reaction:
2Cu2O (s) + Cu2S (s) —— 6Cu (s) + SO2 (g)
Identify the species among the following acting as oxidant and reductant, respectively:

[amp_mcq option1=”Cu(I) and S of Cu2S” option2=”Cu and S of SO2″ option3=”Cu and O of SO2″ option4=”Cu(I) and O of SO2″ correct=”option1″]

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UPSC CAPF – 2023

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In the reaction 2Cu₂O (s) + Cu₂S (s) → 6Cu (s) + SO₂ (g), the oxidation states are as follows:
In Cu₂O, Cu is +1, O is -2.
In Cu₂S, Cu is +1, S is -2.
In Cu, Cu is 0.
In SO₂, S is +4, O is -2.
Cu changes from +1 to 0, so it is reduced. The species causing reduction (oxidant) contains Cu(+1). Both Cu₂O and Cu₂S contain Cu(+1).
S changes from -2 (in Cu₂S) to +4 (in SO₂), so it is oxidized. The species causing oxidation (reductant) is Cu₂S, specifically the S atom within it.
Thus, Cu(I) acts as the oxidant and S of Cu₂S acts as the reductant.

An oxidant (oxidizing agent) is a substance that accepts electrons and is itself reduced. A reductant (reducing agent) is a substance that donates electrons and is itself oxidized. In this reaction, Cu(I) gains electrons to become Cu(0), hence Cu(I) is the oxidant. S(-2) loses electrons to become S(+4), hence S(-2) is the reductant.

This is a self-reduction reaction where the same element (Copper) is present in both reactants and is reduced, while another element (Sulfur) is oxidized. Specifically, Copper from both Cu₂O and Cu₂S is reduced. The sulfur from Cu₂S is oxidized. Therefore, Cu(I) collectively from the reactants acts as the oxidant, and S in Cu₂S acts as the reductant.

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