Problem 146 - A Complete Resource Book in Chemistry for JEE Main

Question

The increasing order of the oxidizing capacity of the oxyacids of chlorine is (a) \(\mathrm{HClO}_{4}<\mathrm{HClO}_{3}<\mathrm{HClO}_{2}<\mathrm{HClO}\) (b) \(\mathrm{HClO}_{3}<\mathrm{HClO}_{4}<\mathrm{HClO}_{2}<\mathrm{HClO}\) (c) \(\mathrm{HClO}_{4}<\mathrm{HClO}_{3}^{*}<\mathrm{HClO}^{2}<\mathrm{HClO}_{2}\) (d) \(\mathrm{HClO}<\mathrm{HClO}_{2}<\mathrm{HClO}_{3}<\mathrm{HClO}_{4}^{2}\)

Step-by-Step Solution

Answer

(d) \(\mathrm{HClO}<\mathrm{HClO}_{2}<\mathrm{HClO}_{3}<\mathrm{HClO}_{4}\) is correct.

Step 1: Understanding Oxidizing Agents

Oxidizing agents are substances that can accept electrons in a chemical reaction. The oxidizing capacity is generally greater when a molecule has more electronegative atoms or when the central atom is in a higher oxidation state. This means that the molecule can more easily pull electrons towards itself.

Step 2: Analyzing Chlorine Oxyacids

The oxyacids of chlorine are \[\mathrm{HClO}, \mathrm{HClO}_{2}, \mathrm{HClO}_{3}, \mathrm{HClO}_{4}\]. In each of these acids, chlorine is in different oxidation states: +1 in \[\mathrm{HClO}\], +3 in \[\mathrm{HClO}_{2}\], +5 in \[\mathrm{HClO}_{3}\], and +7 in \[\mathrm{HClO}_{4}\].The higher the oxidation state of the chlorine, the greater its oxidizing capacity.

Step 3: Increasing Order of Oxidizing Capacity

Based on the oxidation states, the oxidizing capacity increases as follow: \[\mathrm{HClO} \, (\text{+1}) < \mathrm{HClO}_{2} \, (\text{+3}) < \mathrm{HClO}_{3} \, (\text{+5}) < \mathrm{HClO}_{4} \, (\text{+7})\]. This correlates to the chlorine atom's increasing ability to accept electrons as its oxidation state increases.

Step 4: Verifying the Answer

From the given options, option (d) \[\mathrm{HClO}<\mathrm{HClO}_{2}<\mathrm{HClO}_{3}<\mathrm{HClO}_{4}^{2}\] correctly reflects the increasing order of oxidizing capacity. The placement of \[\mathrm{HClO}, \mathrm{HClO}_{2}, \mathrm{HClO}_{3}, \mathrm{HClO}_{4}\], factually aligns with their respective oxidation states.

Key Concepts

Chlorine Oxyacids

Chlorine oxyacids are a group of acids that contain chlorine, oxygen, and hydrogen. They are vital in understanding various chemical reactions, especially those involving redox processes. These oxyacids include:

• Hypochlorous acid \(\mathrm{HClO}\)\
• Chlorous acid \(\mathrm{HClO}_{2}\)\
• Chloric acid \(\mathrm{HClO}_{3}\)\
• Perchloric acid \(\mathrm{HClO}_{4}\)\

The chlorine atom in these acids has varying oxidation states, influencing the acid's properties and reactions. These oxyacids are instrumental in forming bleach and disinfectants, thanks to their strong oxidizing properties. The ability to accept electrons makes them excellent oxidizing agents in many reactions, notably in water disinfection and cleaning products.

Oxidation States

The concept of oxidation states is central in chemistry, especially when dealing with redox reactions. It refers to the imaginary charges atoms would possess if electrons were completely transferred, rather than shared, in compounds.
For chlorine oxyacids, the oxidation state of chlorine progresses from +1 in hypochlorous acid \(\mathrm{HClO}\), to +7 in perchloric acid \(\mathrm{HClO}_{4}\). This increase signifies a greater number of electrons being pulled away from chlorine as the oxidation state rises.
In essence, a higher oxidation state reflects a stronger oxidizing capacity. This is due to the atom’s greater ability to attract electrons, making these substances more reactive in chemical processes.

Chemical Reactions

Chemical reactions involving chlorine oxyacids are often centered around redox processes. Redox, short for reduction-oxidation, involves the transfer of electrons between atoms. It's here where the oxidizing power of chlorine oxyacids really shines.
In a redox reaction, the substance that gains electrons is reduced, while the one that loses electrons is oxidized. Chlorine oxyacids can effectively fulfill the role of oxidizing agents, meaning they facilitate the oxidation of other substances by accepting electrons themselves.

• This makes them pivotal in industrial applications such as bleaching and sanitation.
• Their reactivity and varying oxidation states allow for tailored use based on the specific chemical needs.

The chemical flexibility of chlorine oxyacids comes from their structure and the variable oxidation states, allowing adaptations in chemical protocols depending on the desired outcome.