Problem 27 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following colloids are solvent loving? (a) lyophilic (b) lyophobic (c) hydrophilic (d) none of these

Step-by-Step Solution

Answer

(a) lyophilic and (c) hydrophilic colloids are solvent loving.

Step 1: Understand Colloids

Colloids are mixtures where one substance is dispersed evenly throughout another. In terms of interaction with the solvent, colloids can be classified into two main types: lyophilic and lyophobic.

Step 2: Define Lyophilic Colloids

Lyophilic colloids, also known as 'solvent loving' colloids, have an affinity for the solvent. They form spontaneously when the substance is mixed with a suitable solvent and are stable.

Step 3: Define Lyophobic Colloids

Lyophobic colloids, or 'solvent hating' colloids, do not have an affinity for the solvent. They require special methods to prepare and are less stable than lyophilic colloids.

Step 4: Define Hydrophilic Colloids

Hydrophilic colloids are a type of lyophilic colloid where water is the solvent. These colloids have a strong affinity for water.

Step 5: Identify Solvent Loving Colloids

Based on the definitions, lyophilic (including hydrophilic when water is the solvent) colloids are solvent loving because they have an affinity for solvents and form stable colloids.

Key Concepts

Lyophilic Colloids

Lyophilic colloids, also known as "solvent loving" colloids, have a natural affinity for the solvent in which they are dispersed. These colloids are characterized by their ability to form spontaneously without any external energy input.
When lyophilic colloidal particles are mixed with a suitable solvent, they readily dissolve, and the solutions they form are typically stable over time. This stability is due to the attractive forces between the colloidal particles and the solvent molecules, which prevent the particles from settling or aggregating.
Some common examples of lyophilic colloids include gelatin, starch, and proteins in a solvent like water. Since these materials innately mix well with the solvent, they are often easier to work with in various industrial and culinary applications compared to their lyophobic counterparts.

• Spontaneously form in a suitable solvent
• Stable and do not require special conditions
• Common examples: gelatin, starch, proteins

Lyophobic Colloids

Lyophobic colloids are the opposite of lyophilic colloids; these are often referred to as "solvent hating" colloids. These colloids lack an affinity for the solvent, meaning they do not mix with the solvent spontaneously. Instead, creating a lyophobic colloid usually requires special preparation methods like vigorous shaking, grinding, or using an emulsifying agent.
Since lyophobic colloids do not naturally dissolve in the solvent, they tend to be less stable. Over time, the colloidal particles are more likely to aggregate and separate from the solvent, leading to a breakdown in the colloidal suspension.
Common examples of lyophobic colloids include metal salts in water. These require external energy or the addition of stabilizers to maintain suspension, making them more challenging to manage in practical applications compared to lyophilic colloids.

• Do not naturally mix with solvents
• Less stable and require special preparation
• Common examples: metal salts in water

Hydrophilic Colloids

Hydrophilic colloids are a subset of lyophilic colloids where water is specifically the solvent. As the name suggests, 'hydro' refers to water, and 'philic' means loving. These colloids have a strong affinity for water, and when dispersed in water, they form more stable and uniform solutions.
Their formation occurs spontaneously, just like other lyophilic colloids, owing to their high affinity for water molecules. The stability arises from the interactions between the hydrophilic particles and water, which help disperse the particles evenly in the solution.
Many biological molecules, like proteins and carbohydrates, are examples of hydrophilic colloids. These molecules naturally tend to dissolve in water and are integral to many biological processes. They are also crucial in food industries, as they aid in processes requiring gel formation or thickening.

• Subcategory of lyophilic colloids with water as the solvent
• Spontaneously form stable solutions in water
• Common in biological processes and food industries