Question

Which of the following can act as oxidizing as well as reducing agent?
A. ${O_3}$
B. $HN{O_3}$
C. $S{O_2}$
D. ${H_2}{O_2}$

Answer 1

We know in chemistry we have various oxidation and reduction reactions required to produce various compounds. Oxidation refers to oxidizing a compound with the mechanism of accepting electrons. Reduction refers to reducing a compound with the mechanism of losing or donating electrons.

Complete step by step answer:
We must remember that all the given options above are generally used as catalysts or reagents in reaction procedures. Let us see if the above reagents can act as oxidizing or reducing agents by calculating their number of oxidation. Every element has its different oxidation number in different compounds.
1. ${O_3}$
We know that the oxidation number of oxygen ranges from $- 2$ to $0$ , but only in molecules not as an atom. Hence, in the ozone compound the oxidation number is 0, which means it can gain electrons. Thus, it is a reducing agent.
2. $HN{O_3}$
We know the oxidation number of hydrogen and oxygen is $- 1$ and $- 2$.
Therefore, the oxidation number of nitrogen will be –
$1 + N + 3\left( { - 2} \right) = 0$
On simplification we get,
$\Rightarrow N = + 5$
Since the maximum oxidation number is +5, the nitrogen cannot reduce further. Hence, it can only act as a reducing agent and not an oxidizing agent.
3. $S{O_2}$
Since, we have the oxidation number of oxygen as $- 2$.
Let us calculate for sulphur,
$S + 2\left( { - 2} \right) = 0$
On simplification we get,
$\Rightarrow S = + 4$
Since, the maximum oxidation state of sulphur is +6 and minimum oxidation number is +2. Thus it acts as a reducing agent and oxidation agent as well.
4. ${H_2}{O_2}$
The oxidation number of hydrogen is +1.
Hence, the oxidation number of oxygen will be,
$2 + 2O = 0$
On simplification we get,
$\Rightarrow O = - 1$
Oxygen can reduce to -2 and oxidize to 0, so it can act as oxidizing and reducing agent both.

So, the correct answer is Option C,D.

Note: We have to remember that in a majority of reactions there is oxidation as well as reduction process taking place in the process of reaction by means of gaining or losing electrons. In some reactions the oxidation and reduction can take place simultaneously in the same reaction. Such reactions are called redox reactions, where the reagents can act as both oxidizing as well as reducing agent. The oxidation number plays an important role in this process, which is the key term used to identify the reducing and oxidizing agents.