In which of the following reactions ozone acts as reducing reagent? (a) \(2 \mathrm{HCl}+\mathrm{O}_{3} \rightarrow \mathrm{Cl}_{2}+\mathrm{H}_{2} \mathrm{O}+\mathrm{O}_{2}\) (b) \(\mathrm{BaO}_{2}+\mathrm{O}_{3} \rightarrow \mathrm{BaO}+2 \mathrm{O}_{2}\) (c) \(2 \mathrm{KI}+\mathrm{O}_{3}+\mathrm{H}_{2} \mathrm{O} \rightarrow 2 \mathrm{KOH}+\mathrm{I}_{2}+\mathrm{O}_{2}\) (d) \(\mathrm{PbS}+4 \mathrm{O}_{3} \rightarrow \mathrm{PbSO}_{4}+4 \mathrm{O}_{2}\)

Understanding oxidation states is crucial when studying redox reactions in chemistry. An oxidation state, often referred to as the oxidation number, is an indicator of the degree of oxidation of an atom in a chemical compound. This concept illustrates the number of electrons that may be counted as belonging to the atom or lost by it.

For instance, in its elemental form, an atom has an oxidation state of zero. In compounds or chemical reactions, these oxidation states can change as electrons are transferred between atoms. A negative oxidation state indicates that the atom has gained electrons, while a positive state means it has lost electrons. Recognizing these states is essential for determining the role of substances in redox reactions, such as identifying reducing and oxidizing agents.

Redox reactions are chemical reactions involving the transfer of electrons between two species. These processes are composed of two half-reactions: one for oxidation and one for reduction. In oxidation, an atom or molecule loses electrons, resulting in an increase in oxidation state. Conversely, reduction involves a gain of electrons and a decrease in oxidation state.

Oxidation and reduction always occur simultaneously since electrons transferred from one atom must be accepted by another. The significance of redox reactions is vast, spanning biological systems, industrial processes, and environmental chemistry. A deep comprehension of redox mechanisms is pivotal for mastering concepts in chemistry.

Ozone, with the chemical formula O3, is a powerful oxidizing agent rather than a reducing agent in most chemical reactions. As an oxidizer, ozone readily accepts electrons from other substances. However, in some less common situations, ozone can act as a reducing agent by donating electrons to another species.

This role reversal is typically identified by a change in the oxidation state of ozone in a reaction. But as demonstrated in the provided exercise solutions, if ozone transitions to oxygen gas (O2) without altering its oxidation state, it neither acts as a reducing agent nor as an oxidizer. Exploring how ozone behaves in different chemical environments, especially unusual ones, can be a fascinating and instructive aspect of redox chemistry.

National Eligibility cum Entrance Test (NEET) is a competitive exam for students aspiring to pursue medical and related fields in India. NEET chemistry includes a significant emphasis on understanding chemical reactions, including redox processes. Grasping the concepts of oxidation states, redox reactions, and the behavior of substances like ozone is crucial for NEET candidates.

Since NEET chemistry questions often involve determinations of reducing and oxidizing agents as well as predicting the products of chemical reactions, a strong foundation in these areas can greatly bolster a student's performance. Mastery of these topics not only aids in textbook exercises but is a determinant for success in competitive exams like NEET.