Question

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

Short answer

Statements (a) and (d) are correct.

Step-by-step solution

Analyze Statement (a)

Statement (a) claims that He and Ne do not form clathrates. Clathrates are cage-like structures in which small molecules are trapped inside the cavities of a lattice composed of water molecules. Generally, helium (He) and neon (Ne) do not form clathrates due to their small atomic sizes and low polarizability, which do not allow them to stabilize in the water lattice. Hence, statement (a) is correct.

Evaluate Statement (b)

Statement (b) suggests that \(\mathrm{XeF}_{4}\) and \(\mathrm{SbF}_{4}\) combine to form a salt. \(\mathrm{XeF}_{4}\) (xenon tetrafluoride) is a known compound, but \(\mathrm{SbF}_{4}\) (antimony tetrafluoride) is not commonly synthesized or stable in typical conditions. It is usually in the form of \(\mathrm{SbF}_{5}\) (antimony pentafluoride). Therefore, this statement is false as they do not typically combine to form a stable salt.

Assess Statement (c)

Statement (c) asserts that helium (He) has the highest boiling point in its group. Helium is a noble gas, and among the noble gases, helium actually has the lowest boiling point due to its very low atomic mass and weak dispersion forces. Therefore, statement (c) is not correct.

Investigate statement (d)

Statement (d) states that helium can diffuse through materials such as rubber and polyvinyl chloride. Helium is known for its ability to penetrate through many materials, including rubber and some plastics like polyvinyl chloride, due to its small atomic size. This makes it useful in leak detection applications. Thus, statement (d) is correct.

Key concepts

Clathrates

Clathrates are fascinating chemical structures where small molecules get trapped inside a lattice of host molecules, usually water. Think of clathrates as cages, where the walls are formed by a network of water molecules, creating cavities that can encage other small molecules or gases. However, not all gases can form clathrates. Helium (He) and Neon (Ne) are examples of gases that do not typically form clathrates. This is largely due to their small atomic sizes and low polarizability.

• Small atomic size: Helium and Neon atoms are tiny and can't stabilize within the clathrate cage.
• Low polarizability: This means they can't induce charges within the water molecule lattice to stabilize themselves in the structure.

These reasons make it hard for He and Ne to form stable clathrate compounds, unlike other gases that can more easily fit and stabilize within clathrate cages.

Xenon Tetrafluoride

Xenon Tetrafluoride, represented as \(\mathrm{XeF}_{4}\), is one of the few compounds made from a noble gas. Its formation is due to xenon's ability to form bonds with fluorine, despite being a noble gas, which typically resists reactions because it has a full valence shell.

• Structure: \(\mathrm{XeF}_{4}\) features a square planar geometry with xenon at the center, surrounded by four fluorine atoms.
• Stability: The molecule is stable because of the strong xenon-fluorine bonds but lacks typical ionic character seen in most salts.

While the statement in the exercise mentions \(\mathrm{SbF}_{4}\), it's actually \(\mathrm{SbF}_{5}\) that's more common and known for its stability. Together, \(\mathrm{XeF}_{4}\) and \(\mathrm{SbF}_{4}\) do not usually form typical salts because \(\mathrm{SbF}_{4}\) is not stable under ordinary conditions.

Diffusion of Gases

Diffusion is the process by which gas molecules spread out in response to concentration gradients. Helium is renowned for its exceptional ability to diffuse through various materials, including rubber and polyvinyl chloride (PVC). This quality stems from helium's small atomic size, which allows it to slip through tiny gaps between atoms or molecules in solid materials.

• Applications: Due to helium’s diffusion capacity, it is often used in leak detection, particularly for identifying tiny leaks in sealed systems.
• Materials: Helium can permeate through common polymers like rubber and PVC, making it less ideal for long-term gas containment.

This property is why helium-filled balloons lose their gas more quickly than those filled with other gases—they can diffuse even through the balloon's tight latex structure.

Boiling Point of Noble Gases

The boiling point of noble gases is a key property reflecting their intermolecular forces. Noble gases like helium, neon, and others have very low boiling points because they are monoatomic and interact through weak dispersion forces, also known as Van der Waals forces.

• Helium: Among noble gases, helium has the lowest boiling point at about -269°C (-452°F), close to absolute zero. This is because it has the smallest atomic size and weakest intermolecular forces.
• Trends: As we move down the group in the periodic table, the boiling points of noble gases increase due to stronger dispersion forces, larger atomic size, and increased electron interactions.

These properties make helium ideal for applications requiring very low temperatures, like cryogenics, but it certainly doesn't possess the highest boiling point among noble gases.