Problem 103 - A Complete Resource Book in Chemistry for JEE Main

Question

In Fischer-Ringe's method of separation of noble gas mixture from air, ..... is used. (a) \(90 \% \mathrm{CaC}_{2}+10 \% \mathrm{CaCl}_{2}\) (b) soda lime \(+\) potash solution (c) \(90 \% \mathrm{CaCO}_{3}+10 \%\) urea (d) coconut charcoal

Step-by-Step Solution

Answer

(d) coconut charcoal.

Step 1: Analyze the Method

Fischer-Ringe's method is used to separate noble gases from the air. To achieve this separation, certain absorbent materials are used which can selectively absorb components of air without affecting noble gases.

Step 2: Evaluate the Options

Now, let's consider the given options: (a) is a combination of calcium carbide and calcium chloride, (b) involves soda lime and potash solution, (c) is composed of calcium carbonate and urea, and (d) is coconut charcoal. Usually, noble gases are separated using absorption methods that don't react directly with the stable noble gases.

Step 3: Identify the Best Absorbent

Out of the given options, coconut charcoal (d) is known for its ability to adsorb impurities and non-noble gases under certain conditions, allowing the noble gases to remain unabsorbed. It is commonly used as an adsorbent for this purpose.

Key Concepts

Noble Gases

Noble gases are a group of chemical elements with similar properties found in group 18 of the periodic table. They are known for their remarkable stability due to having complete valence electron shells. This makes them largely inert and non-reactive under standard conditions, a trait that is quite rare among elements. The noble gases include helium ( He ), neon ( Ne ), argon ( Ar ), krypton ( Kr ), xenon ( Xe ), and radon ( Rn ).

Because of their inertness, noble gases are often used in situations where reactions are unwanted. For instance, they are used in light bulbs to prevent the tungsten filament from oxidizing, and in neon signs due to their ability to emit light when electrified. Additionally, noble gases are important in scientific research and various industrial applications involving gas mixtures.

• Helium: Lightest noble gas, often used in balloons and as a cryogenic agent.
• Neon: Known for its vibrant color emissions in neon lighting.
• Argon: Commonly used in welding and protecting industrial processes.
• Krypton: Used in high-performance lighting products.
• Xenon: Utilized in high-intensity lamps.
• Radon: Radioactive, with uses in some medical treatments.

Absorbent Materials

Absorbent materials are substances used extensively in both laboratory and industrial settings to trap or soak up gases, liquids, or other substances. These materials are pivotal in processes involving separation, purification, and filtration.

In the context of separating gases, such as in the Fischer-Ringe's method for noble gases, absorbent materials selectively trap certain components in a mixture, allowing the desired component, in this case, noble gases, to be isolated. This selectivity is reliant on the physical properties of the absorbent, including its surface area, porosity, and chemical affinity.

• High surface area: Greater surface contact improves absorption efficiency.
• Porosity: Highly porous materials allow more substance exchange.
• Chemical affinity: Selective absorption based on desired chemical reactions or affinities.

Absorbent materials can be made from a variety of substances, from natural organics to synthetically-produced compounds, each designed for specific absorption tasks.

Coconut Charcoal

Coconut charcoal is a high-grade absorbent material favored in many industrial applications for its ability to purify air and water. Made from the shells of coconuts, it is a type of activated carbon with numerous tiny pores that significantly increase its surface area, making it extremely effective in trapping impurities.

This material's efficiency stems from its large surface area, which provides ample room for adsorption—a process where contaminants adhere to the surface of the charcoal rather than becoming chemically absorbed. In the Fischer-Ringe's method, coconut charcoal is employed specifically to isolate noble gases from air mixtures by attracting and holding onto other gas impurities, such as oxygen or nitrogen.

• Derived from natural and renewable resources.
• Environmentally friendly and highly effective in adsorbing gases and odors.
• Utilized in water filtration systems and air purification devices.
• Exceptional absorption properties make it ideal for applications like gas separation.

The choice of coconut charcoal in noble gas separation is primarily due to its ability to maintain the purity of these gases by trapping other atmospheric components effectively.