Problem 166 - A Complete Resource Book in Chemistry for JEE Main

Question

Match the following Column-I (a) Sulphur vapour passed through cold water (b) Soap mixed with water above critical micelle concentration (c) White of egg whipped with water (d) Soap mixed with water below critical micelle concentration Column-II (p) Normal electrolyte solution (q) Molecular colloids (r) Associated colloid (s) Macro molecular colloids

Step-by-Step Solution

Answer

(a) matches with (q), (b) with (r), (c) with (s), and (d) with (p).

Step 1: Understanding Column-I Terms

In Column-I, we have certain systems or conditions given: (a) Sulphur vapour passed through cold water creates a heterogeneous mixture. (b) Soap mixed with water above the critical micelle concentration forms micelles. (c) White of egg whipped with water refers to a protein solution, which are typically large molecules. (d) Soap mixed with water below the critical micelle concentration shows individual soap molecules dispersed in water.

Step 2: Understanding Column-II Terms

Column-II describes types of mixtures or solutions: (p) Normal electrolyte solutions consist of ions uniformly dispersed in a liquid. (q) Molecular colloids refer to dispersions of molecules much larger than small ions but smaller than macromolecules. (r) Associated colloids are characterized by the self-association of molecules in a solution. (s) Macromolecular colloids contain large molecules dispersed in a medium, like proteins.

Step 3: Matching (a) with Column-II

The system (a) Sulphur vapour passed through cold water creates a heterogeneous system typical of molecular colloids. It corresponds to (q) Molecular colloids.

Step 4: Matching (b) with Column-II

In (b), soap forms micelles above critical micelle concentration; thus, it behaves as an associated colloid. This corresponds to (r) Associated colloid.

Step 5: Matching (c) with Column-II

White of egg whipped in water contains large protein molecules that form macromolecular colloids. This corresponds to (s) Macromolecular colloids.

Step 6: Matching (d) with Column-II

In (d), soap molecules dispersed below the critical micelle concentration behaves like a normal solution with individual molecules, corresponding to (p) Normal electrolyte solution.

Key Concepts

Heterogeneous mixture

A heterogeneous mixture is a type of mixture where the components are not uniformly distributed and different phases can be observed within the system. In these mixtures, you can often see various substances or particles, making it easy to distinguish the components visually.
For example, when sulfur vapor is passed through cold water, you get a heterogeneous mixture. The sulfur doesn't dissolve uniformly in the water but remains in a distinct phase, often as tiny droplets suspended in the liquid. This type of mixture is quite common in everyday life, like oil shaken with water, where you can clearly see two layers.

• Components are visible and can be easily separated.
• Each substance retains its properties together with the others.

This mixture is different from homogeneous mixtures, like solutions where everything is evenly mixed at a molecular level.

Micelles

Micelles are special structures formed in a solution by surfactant molecules, like soap, when present above a certain concentration known as the critical micelle concentration (CMC). They are tiny, spherical particles where the hydrophobic tails of the surfactant molecules cluster in the center while the hydrophilic heads face the surrounding water.
This structure allows micelles to trap oil, grease, and other non-polar substances at their core, making them effective cleaning agents. When soap is mixed with water above the CMC, micelles form, which is essential for its ability to clean.

• Micelles have a hydrophobic core and a hydrophilic surface.
• They only form in adequate concentrations of soap in water.

Micelles are an excellent example of how molecular structure affects the function of everyday substances.

Macromolecular colloids

Macromolecular colloids are systems where large molecules, such as proteins or synthetic polymers, remain evenly dispersed throughout a solvent. This type of colloid is characterized by the presence of macromolecules that provide stability to the colloid.
When white of egg is whipped with water, it forms a macromolecular colloid because the protein molecules in the egg form a network that traps air, creating a foam-like structure. This kind of colloid is stable due to the size and nature of the macromolecules involved.

• Large molecules ensure even dispersion in the medium.
• Common in biological systems, like blood plasma and gelatin.

Macromolecular colloids are essential for both biological and industrial processes.

Critical micelle concentration

The critical micelle concentration (CMC) is the concentration of surfactants in a solution at which micelles begin to form. Below this concentration, the surfactant molecules exist singly, but above it, they start to assemble into micelles.
The concept of CMC is crucial for understanding how detergents and similar substances work. Soap mixed with water below the CMC exists as individual molecules which can easily interact with water but aren't structured into micelles. As the concentration surpasses the CMC, micelles form, significantly changing the solution's properties, including its cleaning efficiency.

• Critical threshold for micelle formation.
• Greatly influences the properties of the solution.

Understanding the CMC helps in designing and using products that rely on surfactants for effectiveness.