Question

Among the following, identify the compounds which cannot act as both oxidising and reducing agents
A. H₂O₂
B. H₂
C. SO₂
D. Cl₂

Answer 1

Hint: The chemical compound which loses at-least one electron and gets oxidised to reduce other chemical species is called a reducing agent. The chemical compounds which gain at least one electron and get reduced to oxidise other chemical species are called reducing agents.

Complete Step by Step Answer:
H₂O₂ can act as both oxidising and reducing agent because it contains O. It gets oxidised into O₂, acting as a reducing agent and It gets reduced into H₂O, acting as an oxidising agent. The given reaction is-

SO₂ can also act as an oxidising and reducing agent because in SO₂ Sulphur is in a +4 oxidation state so it can gain electrons and get reduced into a +3, +2, +1, O,-1, or -2 oxidation state and it can also lose 2 electrons to attain +6 oxidation state. The reaction is:
$SO_2+{\rm Br}_2+2H_2O\rightarrow\ H_2SO_4+2HBr\ $
In the given reaction SO2 is acting as a reducing agent and S is getting oxidised from a +4 oxidation state to a +6 oxidation state. Now the next reaction is-
$SO_2+2H_2S\rightarrow\ {3S+2H}_2O$
In the given reaction SO₂ is acting as an oxidising agent and S is getting reduced from +4 oxidation state to 0 oxidation state.
As we all know Cl₂ is a good oxidising agent it can get reduced to -1 oxidation state very easily because of being highly electronegative. The reaction is-
$CH_4\ +\ {\rm Cl}_2\rightarrow\ CH_3Cl\ +\ HCl$
In the given reaction the chlorine is getting reduced from a 0 oxidation state to -1 oxidation state acting as an oxidising agent. Now for oxidation-
${\rm Cl}_2+\ H_2O\rightarrow\ HClO\ +\ HCl$
In the given reaction chlorine is oxidised from a 0 oxidation state to +1 oxidation state in HClO acting as an reducing agent. Now for oxidation-
In H₂ since H^- is very unstable and does not form in the reaction it cannot act as oxidising agent but as well all good H⁺ is a good reducing agent.
Thus, Option (B) is correct

Note: Commonly oxidation and reduction is also known as addition of oxygen as oxidation and addition of Hydrogen as reduction. Reaction going through both oxidation and reduction is called redox reaction. Corrosion / rusting of iron is a redox reaction.