Problem 34 - A Complete Resource Book in Chemistry for JEE Main

Question

The presence of fluoride ion in polluted water can be detected by using (a) KI+ starch (b) zirconium alizarin-S dye (c) \(\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}+50 \% \mathrm{H}_{2} \mathrm{SO}_{4}\) (d) sodium nitroprusside

Step-by-Step Solution

Answer

The presence of fluoride ions in polluted water is detected using zirconium alizarin-S dye (option b).

Step 1: Understanding the Problem

We need to determine which reagent or combination is used to detect fluoride ions in polluted water. Options include KI + starch, zirconium alizarin-S dye, \(\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}+50 \% \mathrm{H}_{2}\mathrm{SO}_{4}\), and sodium nitroprusside.

Step 2: Analyze Each Option

- **Option (a) KI + starch**: This combination is typically used in the detection of iodine, not fluoride.- **Option (b) Zirconium alizarin-S dye**: This dye is a known reagent for fluoride detection because it reacts with fluoride ions, changing color.- **Option (c) \(\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}+50 \% \mathrm{H}_{2}\mathrm{SO}_{4}\)**: This mixture is typically used as an oxidizing agent, not specifically for fluoride detection.- **Option (d) Sodium nitroprusside**: This compound is generally used in the detection of cyanide ions, not fluoride.

Step 3: Conclusion

Considering the properties and typical applications of each reagent, zirconium alizarin-S dye is used for detecting the presence of fluoride ions due to its specific reaction and color change when in contact with fluoride ions.

Key Concepts

Zirconium Alizarin-S Dye

Zirconium Alizarin-S Dye plays a crucial role in detecting fluoride ions in polluted water. It's a specialized reagent known for its distinct characteristics when interacting with fluoride. This dye is a complex organic compound that binds with zirconium. When exposed to fluoride ions, the dye undergoes a noticeable color change, which is a signal that fluoride is present. The color change happens because fluoride ions effectively displace the dye in the zirconium complex.
In simple terms, when you add zirconium alizarin-S dye to a sample of water, its color can reveal important clues. If the water contains fluoride ions, the original color of the dye will alter, indicating the presence of fluoride. This makes it a valuable tool in environmental chemistry, helping researchers and environmentalists assess water quality. The ability of zirconium alizarin-S dye to provide visual evidence of fluoride makes it user-friendly and efficient for routine water analysis.

Fluoride Ion Detection

Fluoride ion detection is an important process, especially when considering the health and environmental implications of contaminated water. Fluoride, often present in water naturally, can also contaminate water due to industrial processes or improper waste disposal. It's critical to accurately detect its presence to ensure water safety.
There are multiple methods for detecting fluoride ions, including the use of zirconium alizarin-S dye, ion-selective electrodes, and spectrophotometric techniques. The choice of method depends on factors like sensitivity, cost, and required detection limits. Among these, zirconium alizarin-S dye is notable for its colorimetric response, which simplifies analysis.
By adding zirconium alizarin-S dye to a water sample, observers can visually determine the presence and approximate concentration of fluoride ions based on the resulting color intensity. This method is simple, cost-effective, and provides quick results, making it a popular choice for on-site analysis.

Polluted Water Analysis

Analyzing polluted water requires accurate identification of contaminants, such as fluoride ions, which can pose environmental and health risks. Polluted water often contains various chemicals resulting from industrial activities, agricultural runoff, or waste disposal.
To ensure safety and compliance with environmental standards, water analysis must be thorough and precise. This involves several steps:

• Sampling water from different sources to obtain representative data.
• Detecting and measuring contaminants such as fluoride using methods like zirconium alizarin-S dye.
• Assessing the concentrations of detected substances to compare with safe levels.

Fluoride detection using zirconium alizarin-S dye is particularly valuable in identifying the presence and concentration of fluoride, assisting in assessing potential health risks. This method's visual simplicity and reliability make it a key component in polluted water analysis, supporting efforts to maintain safe water quality and protect environmental health. By incorporating techniques like this, environmental researchers can make informed decisions about water treatment and remediation strategies.