Class 12 Chemistry - TAMILNADU
Solutions
The Solutions chapter in Class 12 Chemistry for Tamil Nadu Samacheer Kalvi explores homogeneous mixtures and their physical properties. Students learn about different types of solutions, concentration units like molarity and molality, and solubility factors. A major focus is placed on colligative properties—such as relative lowering of vapour pressure, elevation of boiling point, depression of freezing point, and osmotic pressure—which depend only on the number of solute particles. The chapter also covers vapor pressure of liquid solutions, Raoult's law, ideal and non-ideal solutions, and abnormal molecular masses determined via the van't Hoff factor. This is a high-scoring, numerical-heavy chapter vital for board exams.
Start Learning FreeKey Concepts
Molarity and Molality
Molarity is the number of moles of solute dissolved per litre of solution, whereas molality is the number of moles of solute per kilogram of solvent.
Raoult's Law
States that for a solution of volatile liquids, the partial vapour pressure of each component in the solution is directly proportional to its mole fraction.
Colligative Properties
Properties of solutions that depend upon the total number of solute particles present in a given amount of solvent, rather than the chemical nature of the solute.
Ideal and Non-Ideal Solutions
Ideal solutions obey Raoult's law over the entire range of concentration, while non-ideal solutions show positive or negative deviations from Raoult's law.
Van't Hoff Factor
A factor 'i' used to account for abnormal molecular masses caused by the association or dissociation of solute particles in solution.
Important Formulas
Board Exam Info
In the Tamil Nadu (Samacheer Kalvi) Class 12 Chemistry board exam, this chapter typically carries around 6 to 8 marks. Questions usually include 1 or 2 mark objective questions, short answers on definitions like Raoult's law, and important 5-mark numerical problems based on colligative properties and molar mass determination.
Frequently Asked Questions
What is the difference between molarity and molality?
Molarity depends on the volume of the solution and changes with temperature because volume changes with temperature. Molality depends on the mass of the solvent and remains independent of temperature.
Why do colligative properties fail for certain solutions?
Colligative properties fail when solutes undergo association or dissociation in solution (like electrolytes such as NaCl), which changes the actual number of particles. This is corrected using the van't Hoff factor.
What are positive and negative deviations in non-ideal solutions?
Positive deviations occur when solute-solvent interactions are weaker than solvent-solvent and solute-solute interactions, leading to higher vapour pressure. Negative deviations occur when interactions are stronger, leading to lower vapour pressure.
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