Class 12 Chemistry - CBSE
Solutions
The Class 12 Chemistry chapter on Solutions explores homogenous mixtures and their physical properties, forming a crucial foundation for physical chemistry. Students learn about different types of solutions, concentration terms like molarity and molality, and the vapor pressure of liquid-liquid solutions governed by Raoult's Law. A major focus is placed on ideal and non-ideal solutions, as well as colligative properties—properties that depend only on the number of solute particles. Mastering abnormal molecular masses and the van't Hoff factor is essential, as this high-scoring chapter frequently appears in CBSE board exams through numerical problems and conceptual reasoning questions.
Start Learning FreeKey Concepts
Henry's Law
States that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the solution at a constant temperature.
Raoult's Law
For a solution of volatile liquids, the partial vapor pressure of each component in the solution is directly proportional to its mole fraction.
Ideal and Non-Ideal Solutions
Ideal solutions obey Raoult's Law over the entire range of concentration, whereas non-ideal solutions show positive or negative deviations from it due to solute-solvent interactions.
Colligative Properties
Properties like relative lowering of vapor pressure, elevation in boiling point, depression in freezing point, and osmotic pressure that depend solely on the number of solute particles.
Van't Hoff Factor (i)
A factor introduced to account for the extent of association or dissociation of solute particles in solution, modifying standard colligative property formulas.
Important Formulas
Board Exam Info
In the CBSE Class 12 Chemistry board exam, the Solutions chapter typically carries around 5 to 7 marks. Questions frequently include numerical problems on molality, freezing/boiling point elevation, and osmotic pressure, alongside conceptual questions about non-ideal solutions and Henry's law applications.
Frequently Asked Questions
What is the difference between molarity and molality?
Molarity depends on the total volume of the solution and changes with temperature, whereas molality depends on the mass of the solvent and remains independent of temperature.
Why do non-ideal solutions show positive or negative deviations?
Positive deviations occur when solute-solvent interactions are weaker than solute-solute and solvent-solvent interactions, while negative deviations occur when they are stronger.
When do we use the van't Hoff factor in numericals?
The van't Hoff factor is used whenever the solute undergoes dissociation (like NaCl breaking into ions) or association (like benzoic acid forming dimers) in the solution.
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