Problem 100 - A Complete Resource Book in Chemistry for JEE Main

Question

Noble gases are sparingly soluble in water, owing to (a) hydrogen bonding (b) dipole-dipole interactions (c) dipole-induced dipole interactions (d) induced dipole-instantaneous dipole interactions

Step-by-Step Solution

Answer

(d) Induced dipole-instantaneous dipole interactions.

Step 1: Understanding Noble Gases

Noble gases are elements found in Group 18 of the periodic table. They are characterized by having a complete valence electron shell, making them chemically inert and nonpolar. This means they do not readily form bonds with other atoms.

Step 2: Consider the Interactions

Solubility of noble gases in water is due to interactions that can occur between the noble gases and the water molecules. Since noble gases are nonpolar, they do not participate in hydrogen bonding or dipole-dipole interactions, which require polar molecules.

Step 3: Exploring Suitable Interaction

The possible interactions left are dipole-induced dipole interactions and induced dipole-instantaneous dipole interactions (also known as London dispersion forces). The dipole-induced dipole interaction arises when a nearby dipole (like water) induces a dipole in the noble gas.

Step 4: Choosing the Correct Interaction

The most suitable interaction for noble gases with water is the induced dipole-instantaneous dipole interactions. These are temporary forces that can also occur between nonpolar atoms and polar molecules, allowing for slight solubility in water.

Key Concepts

Noble Gases

Noble gases are a group of elements found in Group 18 of the periodic table. This includes helium, neon, argon, krypton, xenon, and radon. One of their key characteristics is their lack of reactivity, due to the complete valence electron shell. This

• Makes them chemically inert.
• Prevents them from easily forming compounds or reacting with other elements.

They are also nonpolar, which means they do not carry a charge and therefore do not easily form bonds based on electrical attractions.
Observing their environment, you'll find that noble gases are used in applications that benefit from their inertness, such as lighting and welding. Their non-reactivity is a defining trait that influences their behavior in solutions, such as in water.

Induced Dipole-Instantaneous Dipole Interactions

Induced dipole-instantaneous dipole interactions, commonly known as London dispersion forces, are a type of van der Waals force. Despite noble gases being nonpolar, they can participate in these interactions which allow them to dissolve slightly in polar substances like water. Here's how it works:

• Water, which is polar, can induce a temporary dipole in the noble gas by distorting its electron cloud.
• The instantaneous dipoles occur due to fluctuations in the electron cloud which happen naturally.
• These temporary dipoles can interact weakly with water’s permanent dipoles.

This mechanism underscores that even nonpolar gases can enjoy some solubility in polar solvents, albeit to a limited extent. Despite the weak nature of these interactions, they are significant enough to explain the slight solubility of noble gases.

London Dispersion Forces

London dispersion forces are the weakest of the intermolecular forces but essential in understanding interactions in noble gases. These forces arise due to transient and induced dipoles.
While the electron cloud around an atom is generally spherically symmetric, it can become uneven, creating a momentary dipole. This

• Makes them capable of attracting other atoms temporarily.
• Allows nonpolar atoms or molecules like noble gases to interact weakly with others.

Though minor in effect, these forces play a critical role in accounting for phenomena such as the liquefaction of noble gases and their slight solubility in water. Understanding London dispersion forces helps explain why even gases traditionally known for their inertness can interact at a minor level with other substances.