Question

Justify the following reaction as a redox reaction.

\[\ce{2Na_{(s)} + S_{(s)} -> Na2S_{(s)}}\]

Find out the oxidizing and reducing agents.

Answer 1

1. A redox reaction can be described as electron transfer, as shown below:
   \[\ce{2Na_{(s)} + S_{(s)}->2Na^+ + S^2-}\]
2. Charge development suggests that each sodium atom loses one electron to form Na⁺ and the sulphur atom gains two electrons to form S^2–. This can be represented as follows:
   
3. When Na is oxidized to Na₂S, the neutral Na atom loses electrons to form Na⁺ in Na₂S while the elemental sulphur gains electrons and forms S^2– in Na₂S.
4. Each of the above steps represents a half-reaction which involves electron transfer (loss or gain).
5. The sum of these two half-reactions, or the overall reaction, is a redox reaction.
6. An oxidizing agent is an electron acceptor, and hence, S is an oxidizing agent. A reducing agent is an electron donor, and hence, Na is a reducing agent.