Problem 68 - A Complete Resource Book in Chemistry for JEE Main

Question

Select the correct statement. (a) \(\mathrm{ClO}_{2}\) is the anhydride of \(\mathrm{HClO}_{2}\) and \(\mathrm{HClO}_{3}\) (b) \(\mathrm{I}_{2} \mathrm{O}_{5}\) is used in the quantitative estimation of \(\mathrm{CO}\) (c) \(\mathrm{Cl}_{2} \mathrm{O}\) and \(\mathrm{ClO}_{2}\) are used as bleaching agents and as germicides (d) all of the these are correct

Step-by-Step Solution

Answer

Statement (b) is correct.

Step 1: Understanding Anhydrides

An anhydride is a compound that can form an acid or a base when it reacts with water. (a) To verify if \(\mathrm{ClO}_{2}\) is the anhydride of \(\mathrm{HClO}_{2}\) and \(\mathrm{HClO}_{3}\), we need \(\mathrm{ClO}_{2} + \text{H}_2\mathrm{O}\) to form possibly \(\mathrm{HClO}_{2}\) or \(\mathrm{HClO}_{3}\). Normally, \(\mathrm{ClO}_{2}\) forms hypochlorous acids, not specifically dichlorous or chloric acid. Thus, statement (a) is incorrect.

Step 2: Evaluating Estimation Use of Iodine Pentoxide

\(\mathrm{I}_2\mathrm{O}_5\) is known to react with carbon monoxide (\(\mathrm{CO}\)) to yield carbon dioxide (\(\mathrm{CO}_2\)) and iodine (\(\mathrm{I}_2\)). (b) This reaction is utilized in the quantitative estimation of carbon monoxide as it allows for the measurement of \(\mathrm{CO}\) based on the amount of \(\mathrm{I}_2\) produced. Hence, statement (b) is correct.

Step 3: Checking Cl2O and ClO2 Uses

Both \(\mathrm{Cl}_2\mathrm{O}\) (dichlorine monoxide) and \(\mathrm{ClO}_{2}\) (chlorine dioxide) are used industrially and for water treatment purposes. (c) However, \(\mathrm{Cl}_2\mathrm{O}\) is not commonly used in modern contexts as a bleaching agent or germicide; \(\mathrm{ClO}_{2}\) is used for bleaching and disinfection. Thus, statement (c) is incorrect.

Key Concepts

Anhydrides

Anhydrides are fascinating compounds in chemistry, particularly because of their ability to form acids or bases when they react with water. They are often derivatives of acids, where the water molecule is removed from the acid. This removal often involves two acid molecules combining to release one water molecule. Consequently, when we add water back, they reform the original acid.
For example, sulfur trioxide ( SO_3 ) is the anhydride of sulfuric acid ( H_2 SO_4 ). Its natural reaction with water yields sulfuric acid, a crucial chemical in various industrial processes. Understanding the behavior of anhydrides is vital for comprehending how many biological and chemical systems operate.
In our context, while ClO_2 might resemble behavior for some acids, it does not specifically act as an anhydride for HClO_2 or HClO_3 when reacted with water, highlighting the specificity of chemical reactions involving anhydrides.

Quantitative Estimation

Quantitative estimation in chemistry involves determining the amount or concentration of a substance in a sample. One exceptional method used is the reaction of iodine pentoxide ( I_2 O_5 ) with carbon monoxide ( CO ). Here, I_2 O_5 is employed to oxidize CO into carbon dioxide ( CO_2 ), producing iodine ( I_2 ) as a byproduct: I_2 O_5 + 5CO → I_2 + 5CO_2 .
This reaction is immensely practical because the amount of I_2 formed is directly proportional to the concentration of CO present. By measuring the iodine produced, chemists can accurately quantify how much carbon monoxide was in the sample. This is a robust method in analytical chemistry for its precision and reliability.

Bleaching Agents

Bleaching agents are substances used to remove color, whiten, or disinfect materials. They play a crucial role in industries such as paper, textile, and water treatment. Among common bleaching agents, chlorine dioxide ( ClO_2 ) stands out due to its effectiveness and safety profile.
ClO_2 works by breaking the bonds of colored molecules, thus making them colorless. Its use extends beyond bleaching; it's an effective disinfectant, eliminating bacteria and viruses without leaving toxic byproducts. This is why it's often used in water treatment to ensure our water is free from pathogens. Its dual role as a bleaching agent and germicide makes chlorine dioxide incredibly versatile for various applications.

Germicides

Germicides are agents that kill germs and pathogens, including bacteria, viruses, and fungi. These compounds are essential for maintaining public health, especially in sanitation and medical fields.
Chlorine dioxide ( ClO_2 ) serves as a powerful germicide, renowned for its efficacy in low concentrations. It works by disrupting the cell walls and internal components of microorganisms, rendering them inactive. Unlike some other disinfectants, ClO_2 does not produce harmful byproducts, making it a safer choice for many disinfection scenarios, including treating drinking water.
Despite Cl_2 O being mentioned as a possible agent for similar uses, ClO_2 is far more prevalent today due to its superior effectiveness and safety standards.