Question

Which of the following elements have the ability to behaves as both oxidising and reducing agents?

• A. H₂SO₄
• B. SO₂
• C. H₂S
• D. HNO₃

Answer 1

The correct option is B

SO₂

In $S{O}_2$, sulphur has +4 oxidation state and in $H_{2}S{O}_4$, Sulphur exhibits its highest oxidation state of +6 where it acts as oxidising agent. On the other hand - in $H_{2}S$, sulphur exists in its lowest -2 oxidation state where it acts as a reducing agent. Thus, we can surmise that $S{O}_2$ could act as both an oxidising agent as well as a reducing agent.

$C{l}^{-}$ is the reducing agent because it is oxidized and loses one electron (starting with an oxidation state of -1 in the $C{l}^{-}$ ions and increasing to 0 in $C{l}_2$). $C{u}^{2+}$(aq) is the oxidizing agent because it gains two electrons, decreasing from an oxidation state of +2 in $C{u}^{2+}$(aq) to an oxidation state of 0 in Cu(s).

$Z{n}^{2+}$ is the reducing agent because it is oxidized and loses two electrons.