Problem 89 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following statements are correct? (1) Temporary hardness of water is due to the presence of bicarbonates of calcium and magnesium in it (2) Permutit is artificial zeolite (3) \(\mathrm{H}_{2} \mathrm{O}_{2}\) acts as an oxidizing agent in the following reaction $$ \mathrm{Cl}_{2}+\mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow \mathrm{O}_{2}+2 \mathrm{HCl} $$ (4) \(\mathrm{H}_{2} \mathrm{O}_{2}\) is used a bleaching agent for delicate textiles. (a) 1,2 and 3 (b) 1,2 and 4 (c) 2,3 and 4 (d) 1,3 and 4

Step-by-Step Solution

Answer

The correct statements are 1, 2, and 4. So, the answer is (b) 1, 2, and 4.

Step 1: Analyze Statement 1

Temporary hardness of water is primarily caused by the bicarbonates of calcium and magnesium. These bicarbonates dissolve in water and can be removed by boiling, which decomposes them into carbonate, water, and carbon dioxide. Thus, statement 1 is correct.

Step 2: Evaluate Statement 2

Permutit is indeed a type of artificial zeolite. Zeolites are used in water softening processes by exchanging sodium ions with calcium and magnesium ions. Therefore, statement 2 is correct.

Step 3: Assess Statement 3

In the given reaction, \[ \mathrm{Cl}_{2} + \mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow \mathrm{O}_{2} + 2 \mathrm{HCl} \]Hydrogen peroxide \( \mathrm{H}_{2} \mathrm{O}_{2} \) acts as an oxidizing agent because it accepts electrons from \( \mathrm{Cl}_{2} \), converting it into \( 2 \mathrm{HCl} \), and reduces itself to \( \mathrm{O}_{2} \). Hence, statement 3 is correct.

Step 4: Verify Statement 4

Hydrogen peroxide is commonly used as a bleaching agent because it can decompose to form "active oxygen" which has strong bleaching properties. It is suitable for delicate textiles due to its mildness and effectiveness. Therefore, statement 4 is correct.

Step 5: Conclusion

Based on the analysis of all four statements, statement 1, statement 2, statement 3, and statement 4 are correct. Therefore, the correct answer is option (b) 1, 2, and 4.

Key Concepts

Water Hardness

Water hardness is all about the minerals dissolved in your water. When water contains high levels of calcium and magnesium salts, it's referred to as "hard". There are two types of hardness in water:

• Temporary Hardness: This results from bicarbonates of calcium and magnesium. The good news is, you can remove this hardness simply by boiling the water. During boiling, bicarbonates break down, resulting in the formation of carbonate, water, and carbon dioxide.
• Permanent Hardness: This type remains even after boiling. It is due to sulfates, chlorides, and nitrates of calcium and magnesium.

Understanding these differences helps in finding the right methods to soften water when needed.

Zeolites and Water Softening

Zeolites play a fascinating role in making hard water soft. Consider them the unsung heroes of water treatment.

Zeolites are natural minerals, but we can also engineer artificial ones. Permutit, which is one type of artificial zeolite, is widely used in the water softening process. The magic lies in their ability to exchange ions. When hard water passes through zeolites, the calcium and magnesium ions swap places with sodium ions from the zeolite. This exchange reduces water hardness, making it more usable for various applications. This process is eco-friendly, efficient, and helps in maintaining appliance longevity.

Hydrogen Peroxide as Oxidizing Agent

Hydrogen peroxide, \( \mathrm{H}_{2} \mathrm{O}_{2}\), is like the powerhouse of gentle chemical reactions. In various reactions, it often acts as an oxidizing agent, meaning it helps substances lose electrons, while it gets reduced itself.

In the reaction \(\mathrm{Cl}_{2} + \mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow \mathrm{O}_{2} + 2 \mathrm{HCl}\), chlorine changes into hydrogen chloride due to the oxygen power of \( \mathrm{H}_{2} \mathrm{O}_{2}\). Such oxidizing actions are essential in many cleaning and purification processes. Hydrogen peroxide is favorable due to its ability to break down into harmless water and oxygen over time.

Bleaching Agents in Chemistry

Bleaching agents have the magical ability to make things whiter and brighter. They achieve this by breaking down the chemical bonds of colors.

Among these agents, hydrogen peroxide stands out, especially when it comes to gentler applications. It's commonly employed for bleaching delicate textiles, thanks to its mild nature. When \( \mathrm{H}_{2} \mathrm{O}_{2}\) decomposes, it releases oxygen, which attacks the bonds of stains and colors, effectively "bleaching" them away. This attribute makes it invaluable not just in textile industries, but also in paper production and household cleaning products. Bleaching isn't just about lightening colors; it's also about hygiene and sanitation.