Problem 125 - A Complete Resource Book in Chemistry for JEE Main

Question

Which among the following statements is/are correct here: (a) He and Ne do not form clathrate (b) \(\mathrm{XeF}_{4}\) and \(\mathrm{SbF}_{5}\) combine to form salt (c) He has highest boiling point in its group (d) He diffuses through rubber and polyvinyl chloride

Step-by-Step Solution

Answer

Correct statements: (a), (b), and (d).

Step 1: Analyze Option (a)

He (Helium) and Ne (Neon) do not form clathrates because clathrates typically form with gases that can be trapped by the lattice of water molecules. Helium and neon do not fit well enough into the water lattice to form clathrates due to their small size and low polarizability. Therefore, statement (a) is correct.

Step 2: Analyze Option (b)

\(\mathrm{XeF}_4\) and \(\mathrm{SbF}_5\) can combine to form a salt. This occurs because \(\mathrm{XeF}_4\) acts as a Lewis base and can donate fluoride to \(\mathrm{SbF}_5\), which acts as a Lewis acid, forming a complex salt of the form \(\mathrm{XeF}_3^+SbF_6^-\). Hence, statement (b) is correct.

Step 3: Analyze Option (c)

In the group of noble gases, helium actually has the lowest boiling point compared to other members like neon, argon, krypton, and xenon. This is due to helium's very weak interatomic forces. Therefore, statement (c) is incorrect.

Step 4: Analyze Option (d)

Helium is known for its small atomic size and low atomic mass, which allows it to diffuse through materials such as rubber and polyvinyl chloride. This is a unique property that makes helium difficult to contain. Thus, statement (d) is correct.

Key Concepts

Clathrate Formation

Clathrate formation is a fascinating phenomenon where gas molecules are trapped within a lattice of host molecules. These structures are often related to water, forming a cage-like structure that encloses the gas molecules. However, not all gases can form clathrates. For instance, noble gases like helium and neon do not form clathrates. This is primarily due to their small atomic sizes and low polarizabilities, which prevent them from fitting properly within the water lattice.

• Gases that form clathrates are generally larger and more polarizable.
• The effectiveness of clathrate formation often depends on the ability of the gas to interact with the water lattice.

Thus, because helium and neon do not fit these criteria, they are unable to participate in clathrate formation.

Lewis Acid-Base Reaction

In the realm of chemistry, a Lewis acid-base reaction involves the transfer of an electron pair, where a Lewis acid accepts and a Lewis base donates. A classic example is the combination of \(\mathrm{XeF}_4\) and \(\mathrm{SbF}_5\). Here, \(\mathrm{XeF}_4\) acts as a Lewis base as it can donate a pair of electrons from a fluoride ion to the \(\mathrm{SbF}_5\), which acts as the Lewis acid by accepting the electron pair. This reaction results in the formation of a complex salt, \(\mathrm{XeF}_3^+ SbF_6^-\).

• Lewis acids are electron pair acceptors.
• Lewis bases are electron pair donors.
• This interaction often leads to the formation of a complex with distinct properties.

Understanding this interaction is crucial to predicting the behavior of various chemical species in reactions.

Boiling Point Trends

Noble gases exhibit interesting boiling point trends across the group. Helium, in particular, has the lowest boiling point among noble gases. This characteristic is due to its extremely weak interatomic forces. Unlike other noble gases such as neon, argon, krypton, and xenon, helium remains in a gaseous state even at very low temperatures because minimal energy is needed to overcome these weak forces.

• Interatomic forces play a key role in determining boiling points.
• Weak forces in helium lead to its low boiling point compared to other noble gases.
• Boiling points generally increase with atomic mass in the noble gases group.

This phenomenon highlights the unique nature of element interactions within the periodic table.

Gas Diffusion in Materials

Gas diffusion through materials depends on several factors, including the size and mass of the gas atoms or molecules. Helium is a small and light atom, which gives it the remarkable ability to diffuse through materials quickly. In particular, helium can permeate through rubber and polyvinyl chloride (PVC). This property poses practical challenges since it makes containing helium difficult.

• Helium's small size allows it to pass through tiny pores in materials.
• Diffusion rates can impact material selection in various applications.
• Understanding diffusion is important in industries where gas containment is crucial.

The study of gas diffusion gives insights into the behavior of gases in varying material environments and influences technological advancements.