Problem 84 - A Complete Resource Book in Chemistry for JEE Main

Question

When water is allowed to freeze in the presence of \(\mathrm{Ar}\), Kr or Xe under pressure then (a) atoms to noble gas (G) get trapped in the crystal lattice of ice giving clathrates corresponding to the composition \(8 \mathrm{G} .26 \mathrm{H}_{2} \mathrm{O}\) (b) these are called noble gas hydrates (c) both are correct here (d) all are incorrect here

Step-by-Step Solution

Answer

Option (c) both are correct here.

Step 1: Understand Noble Gas Clathrates

Noble gas clathrates are compounds where noble gas atoms are trapped in the crystal lattice of another substance, in this case, ice. This phenomenon often occurs when water freezes in the presence of noble gases like Ar, Kr, or Xe under pressure.

Step 2: Analyze Statement (a)

Statement (a) claims that noble gas atoms like Ar, Kr, or Xe get trapped in the ice structure, forming clathrates with a composition of \(8 \mathrm{G} .26 \mathrm{H}_2\mathrm{O}\). This matches the typical ratio found in ice clathrates for noble gases, hence this statement is correct.

Step 3: Analyze Statement (b)

Statement (b) states that the compounds formed, with noble gas atoms in the ice lattice, are called noble gas hydrates. This is accurate as clathrates with noble gases are specifically termed as noble gas hydrates.

Step 4: Evaluate Combined Statements

Both statements (a) and (b) are correct individually. Consequently, option (c), which asserts that both statements are correct, is also correct.

Key Concepts

Crystal Lattice Trapping

Crystal lattice trapping is a fascinating concept where atoms or molecules become confined within the regular, repeating pattern of a crystal structure. Imagine trying to catch a tiny marble within a mesh ball. The marble represents the atoms, while the mesh is the orderly, geometric lattice of the crystal.
In the case of noble gas clathrates, noble gases like Argon (Ar), Krypton (Kr), or Xenon (Xe) are the small marbles. They get trapped inside the "cages" formed by the ice molecules when water freezes under pressure. This structure is incredibly stable, allowing gases to be held in place within the solid ice.

• Water molecules form a crystal lattice as they freeze.
• Noble gas atoms are captured within the octahedral cavities between water molecules.
• These ‘cages’ are highly structured and offer great stability.

The concept of crystal lattice trapping offers insight into the behavior of gases and the capacity of solid forms, like ice, to capture and store these gases in unique structural formats.

Noble Gas Hydrates

Noble gas hydrates are intriguing compounds where noble gases are held within water's crystalline structures. This occurs when gas molecules are encased within ice. The presence of noble gases in the crystal lattice forms what are known as clathrate hydrates.
These hydrates display unique properties, such as maintaining gas integrity even in solid form. They occur naturally and can be synthesized under lab conditions by freezing water in the presence of these gases.

• The term "hydrate" refers to the incorporation of water molecules within the compound.
• Noble gases serve as guest molecules imprisoned in host water lattices.
• The structure permits noble gas atoms to remain stable within the water matrix.

The study of noble gas hydrates is essential for understanding natural processes in oceans and for potential future energy storage solutions.

Gas-Lattice Composition

In clathrates, the composition relates to the number of gas molecules trapped in relation to the water molecules. For noble gas clathrates, the typical formula is written as \(8\mathrm{G}.26\mathrm{H}_2\mathrm{O}\), where:

• \(\mathrm{G}\) is the noble gas atom.
• \(\mathrm{H}_2\mathrm{O}\) represents the water molecules forming the lattice.

This ratio indicates that there are 8 molecules of gas for every 26 molecules of water, providing stability to the crystal structure. The formation of such clathrates requires specific conditions of high pressure and low temperature, which are crucial for the proper entrapment and arrangement of gas molecules within the icy lattice. Understanding this composition helps in predicting the behavior and stability of clathrates under various environmental conditions.

Chemistry Education

Chemistry education plays a crucial role in helping students comprehend concepts like clathrates and lattice trapping. By breaking down these complex ideas into simpler terms, educators can foster a better understanding in students.
Effective teaching of chemistry involves a few key strategies:

• Use of visual aids to illustrate molecular structures and trapping.
• Hands-on experiments to visualize clathrate formation.
• Real-world examples to connect textbook concepts to everyday scenarios.

In bridging the gap between theoretical knowledge and practical understanding, educators can enhance student engagement and interest in the chemistry of gases and solid structures.

JEE Chemistry Concepts

The Joint Entrance Examination (JEE) demands a solid understanding of chemical properties and phenomena, such as noble gas clathrates. For students preparing for the JEE exam, it is crucial to grasp these concepts thoroughly.
Key aspects of JEE chemistry related to clathrates include:

• Understanding the molecular interactions within clathrate hydrates.
• Recognizing the impact of pressure and temperature on clathrate formation.
• Analyzing the structural stability offered by different gas compositions.

By mastering these foundational concepts, students can approach the chemistry section of the JEE with confidence, understanding not just the facts but the underlying principles that govern the behavior of gases in solid matrices.