Class 12 Chemistry - TELANGANA
Solutions
The 'Solutions' chapter in Class 12 Chemistry for Telangana (TSBSE) students explores homogeneous mixtures of two or more components. It covers types of solutions, concentration expressions like molarity, molality, and mole fraction, and solubility of gases and solids in liquids governed by Henry's law. A major portion focuses on colligative properties—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 concludes with abnormal molar masses and the Van 't Hoff factor, making it highly scoring and crucial for board exams.
Start Learning FreeKey Concepts
Molarity (M)
Defined as the number of moles of solute dissolved in one litre of solution. It varies with temperature due to volume change.
Molality (m)
Defined as the number of moles of solute dissolved in one kilogram of solvent. It is independent of temperature as it involves mass.
Henry's Law
States that the partial pressure of a gas in vapour phase is proportional to the mole fraction of the gas in the solution.
Raoult's Law
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 number of solute particles relative to the total number of particles present, not on their nature.
Van 't Hoff Factor (i)
Ratio of the normal molar mass to the abnormal molar mass, used to account for association or dissociation of solute particles.
Important Formulas
Board Exam Info
In the Telangana (TSBSE) Class 12 Chemistry board examinations, the 'Solutions' chapter typically carries around 4 to 6 marks. Questions usually include 2-mark short answer questions on concentration terms or Henry's law, and a 4-mark or 6-mark numerical problem based on colligative properties or the Van 't Hoff factor.
Frequently Asked Questions
Why is molality preferred over molarity while expressing concentration?
Molality involves mass of the solvent, which does not change with temperature, whereas molarity involves volume of the solution, which changes with temperature.
What is the difference between ideal and non-ideal solutions?
Ideal solutions obey Raoult's law over the entire range of concentration with zero enthalpy and volume change of mixing. Non-ideal solutions do not obey Raoult's law and show deviations (positive or negative).
How does the Van 't Hoff factor affect colligative property formulas?
When a solute undergoes association or dissociation, the number of particles changes. The Van 't Hoff factor 'i' is multiplied by the right side of colligative property equations to correct the calculated molar mass.
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