The ions responsible for the bleaching action of bleaching powder and the ions responsible for loss of bleaching action of bleaching powder due to the storage for long time respectively are (a) \(\mathrm{Cl}^{-}, \mathrm{OCl}^{-}\) (b) \(\mathrm{OCl}^{-}, \mathrm{Cl}^{-}\) (c) \(\mathrm{OCl}^{-}, \mathrm{ClO}_{3}^{-}\) (d) \(\mathrm{Cl}^{-}, \mathrm{ClO}^{-}\)

Calcium hypochlorite, often known to chemistry students as 'bleaching powder', plays a pivotal role in common chemical treatments, especially as a disinfectant and a bleaching agent. In its pure form, it is a white granular powder with the chemical formula \( \mathrm{Ca(OCl)_2} \).

It's important to understand that when calcium hypochlorite is added to water, it releases hypochlorite ions \( \mathrm{OCl}^- \) into the solution. These ions are the primary agents responsible for the oxidative removal of color from materials and for killing bacteria and other pathogens in disinfecting processes. While calcium hypochlorite is an effective bleaching agent, attention should be paid to its storage as it can deteriorate over time, primarily through the reaction with carbon dioxide in the air.

The hypochlorite ion \( \mathrm{OCl}^- \) is a key player in the chemistry of bleaching powder. It is this anion that lends the potent oxidative ability to the compound calcium hypochlorite. When used as a bleaching agent, the hypochlorite ion acts on substances by breaking chemical bonds within chromophores—the parts of molecules responsible for color. This disrupts the absorption of visible light and results in a decolorizing effect.

However, its high reactivity also means that it is susceptible to decomposition, especially when exposed to sunlight or when stored improperly over a long period. Decomposition leads to a decreased concentration of \( \mathrm{OCl}^- \) ions, diminishing the bleaching powder's effectiveness. This illustrates the significance of not just the chemical itself, but of the factors affecting its longevity and reactive capabilities.

An oxidation reaction is a chemical process in which a substance loses electrons. This is a crucial concept to grasp when discussing bleaching powder's chemical properties, as the hypochlorite ion \( \mathrm{OCl}^- \) acts as an oxidizing agent. In the world of bleaching, this means that the hypochlorite ion accepts electrons from the colored substances, thereby 'oxidizing' them and removing their color.

Oxidation reactions are not just limited to bleaching—they are fundamental to various other chemical processes, including corrosion, combustion, and metabolism. When teaching this topic, it's beneficial to use examples that relate to students’ everyday experiences, such as rust forming on metal (corrosion) or a campfire burning (combustion). This practical link can help students better understand and remember the concept of oxidation reactions.