Introduction to Solutions and Colligative Properties for JEE Main

The chapter Solutions and Colligative Properties is an important part of Class 12 Chemistry and carries significant weightage in JEE Main examinations. This chapter mainly focuses on the behavior of solutes and solvents, concentration terms, vapor pressure, and properties that depend on the number of particles present in a solution.

For JEE Main aspirants, this chapter is considered scoring because most questions are numerical and formula-based. With proper understanding and regular practice, students can easily secure full marks from this topic.

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What Is a Solution?

A solution is a homogeneous mixture of two or more substances. It consists of:

• Solvent – component present in larger amount

• Solute – component present in smaller amount

Solutions can exist in all three physical states:

• Solid solutions

• Liquid solutions

• Gaseous solutions

JEE Main frequently tests the classification and examples of solutions.

Types of Solutions

Based on the physical state of solute and solvent, solutions are classified as:

• Solid in solid

• Solid in liquid

• Liquid in liquid

• Gas in liquid

• Gas in gas

Understanding real-life examples is helpful for conceptual MCQs.

Concentration Terms in Solutions

Concentration terms form the backbone of numerical problems in JEE Main.

Important concentration expressions include:

• Mass percentage

• Volume percentage

• Mole fraction

• Molarity

• Molality

• Parts per million (ppm)

Among these, mole fraction and molality are widely used in colligative properties.

Solubility of a Gas in a Liquid

The solubility of gases in liquids depends on:

• Pressure

• Temperature

• Nature of gas and solvent

Henry’s Law explains the relationship between pressure and solubility of gases.

JEE Main often asks formula-based questions or conceptual MCQs from Henry’s law.

Vapour Pressure of Liquid Solutions

Vapour pressure is the pressure exerted by vapors of a liquid at equilibrium.

Key concepts:

• Vapour pressure of pure solvent

• Vapour pressure of solution

• Effect of non-volatile solute

Understanding vapour pressure is essential to study Raoult’s Law.

Raoult’s Law

Raoult’s Law states that:

The partial vapour pressure of each component in a solution is directly proportional to its mole fraction.

This law is applicable mainly to ideal solutions.

JEE Main questions test:

• Mathematical application of Raoult’s law

• Vapour pressure lowering

• Comparison of solutions

Ideal and Non-Ideal Solutions

Ideal solutions:

• Obey Raoult’s law over entire concentration range

• No heat change during mixing

• No volume change during mixing

Non-ideal solutions show:

• Positive deviation

• Negative deviation

Understanding deviation types is important for assertion-reason questions.

Colligative Properties – An Overview

Colligative properties are properties that depend only on the number of solute particles, not their nature.

There are four major colligative properties:

1. Relative lowering of vapour pressure

2. Elevation of boiling point

3. Depression of freezing point

4. Osmotic pressure

These topics are highly important for numerical problems in JEE Main.

Relative Lowering of Vapour Pressure

This property is directly proportional to the mole fraction of solute.

Key focus areas:

• Mathematical derivation

• Relationship with Raoult’s law

• Numerical applications

Elevation of Boiling Point

When a non-volatile solute is added:

• Boiling point of solution increases

Formula used:
ΔTb = Kb × m

Where:

• Kb = Molal elevation constant

• m = Molality

JEE Main often asks direct numerical questions from this formula.

Depression of Freezing Point

Addition of solute lowers the freezing point of solvent.

Formula:
ΔTf = Kf × m

This topic is commonly used to calculate:

• Molar mass of solute

• Degree of dissociation

Osmotic Pressure

Osmotic pressure is the pressure required to stop the flow of solvent through a semipermeable membrane.

Formula:
π = CRT

This property is very important for:

• Biomolecules

• Reverse osmosis

• Determination of molar mass

JEE Main frequently asks questions based on osmotic pressure.

Abnormal Molar Mass and van’t Hoff Factor

When solute particles dissociate or associate:

• Observed colligative properties change

van’t Hoff factor (i) accounts for this deviation.

Understanding this concept is crucial for advanced numerical problems.

Numerical Problem-Solving Strategy for JEE Main

• Memorize all formulas

• Practice unit conversions carefully

• Focus on molality-based formulas

• Identify solute behavior (association/dissociation)

• Solve previous year questions

Why Study Solutions and Colligative Properties from Studentbro.in?

Studentbro.in offers:

• Clear concept explanations

• Step-by-step numerical solutions

• Formula sheets

• MCQs and PYQs

• Exam-oriented study material

The content is designed specifically for JEE Main pattern, helping students maximize their score.

Conclusion

The Solutions and Colligative Properties chapter is one of the most scoring chapters in Class 12 Chemistry for JEE Main. Strong conceptual clarity combined with numerical practice can help students secure easy marks.

With structured notes, formulas, and practice questions, Studentbro.in makes learning this chapter simple, effective, and exam-ready.