Problem 123 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following interface cannot be obtained? (a) Solid-liquid (b) Liquid-liquid (c) Liquid-gas (d) Gas-gas

Step-by-Step Solution

Answer

(d) Gas-gas interface cannot be obtained as gases mix completely.

Step 1: Understand the Problem

The problem asks us to identify which type of interface cannot exist between any two materials or phases among the given options.

Step 2: Define Interfaces

In science, an interface is a common boundary or surface where different phases meet, such as between a solid and a liquid or a liquid and a gas.

Step 3: Analyze Each Option

Review each option to determine its feasibility: - (a) Solid-liquid: Commonly exist, e.g., ice-water. - (b) Liquid-liquid: Commonly exist, e.g., oil-water. - (c) Liquid-gas: Commonly exist, e.g., water-air. - (d) Gas-gas: Typically, gases mix homogeneously, not forming a distinct boundary or interface.

Step 4: Identify Infeasible Interface

Gases tend to mix completely in all proportions, not forming a boundary. Thus, a gas-gas interface is not typically observed.

Step 5: Conclusion

The type of interface that cannot be obtained is a gas-gas interface.

Key Concepts

Solid-Liquid Interface

Solid-liquid interfaces are common occurrences in nature and science. They are the boundaries formed when a solid comes in contact with a liquid. Think about an ice cube in a glass of water or a metal spoon touching hot soup. These are everyday examples of solid-liquid interfaces.

At this interface, several interactions are taking place:

• Thermal exchange: Heat can transfer from the hotter phase to the cooler phase.
• Molecular exchange: Solutes in the liquid can get absorbed onto the solid surface.
• Phase change: If conditions are right, the solid might melt or the liquid might freeze.

In industrial settings, understanding these interfaces is crucial. For example, in crystal growth, the properties of solid-liquid interfaces influence the quality of materials produced.

Liquid-Liquid Interface

Liquid-liquid interfaces arise when two immiscible liquids meet, meaning they do not easily mix. An example is oil floating on water. Despite both being liquids, differences in polarity or density prevent them from forming a single homogeneous phase.

These interfaces are fascinating for several reasons:

• Surface tension: This is the force that acts at the interface, impacting the shape and stability of the boundary.
• Emulsions: By adding surfactants, these interfaces can become unstable, causing the liquids to form mixtures, such as vinaigrettes or creams.
• Applications: In chemistry and biology, liquid-liquid interfaces play roles in processes like extraction and purification.

Liquid-Gas Interface

Liquid-gas interfaces are everywhere. They are at play when water evaporates or when clouds form raindrops. The transition between a liquid phase and gas phase creates distinct layers marked by differences in density and molecular behavior.

Key aspects include:

• Evaporation and condensation: At these interfaces, liquids can transform into gases and vice versa, essential processes in the water cycle.
• Aeration in water bodies: Oxygen dissolves in water at these interfaces, crucial for aquatic life.
• Surface phenomena: Activities like surfactant adsorption occur, affecting how the liquid spreads or bubbles form.

Such interfaces are critical in environmental science and industry. They influence everything from weather patterns to the efficiency of sprays and aerosols.

Gas-Gas Non-Interface

A gas-gas non-interface refers to the absence of a distinct boundary between two gases. Unlike solids and liquids, gases mix completely when combined. For instance, when you breathe air, different gases like oxygen and nitrogen coexist without separate layers.

Why do gases form non-interfaces?

• Diffusion: Gas molecules move rapidly and spread evenly through available space.
• Intermolecular forces: Gases exhibit weak interactions, facilitating easy mixing rather than separation.
• Homogeneity: Even when two different gases are present, they will distribute evenly, creating a homogeneous mixture.

This understanding is vital in fields like atmospheric science, where predicting gas behavior helps in modeling climate and weather conditions. It also underpins industrial processes such as gas blending and air purification.