Class 12 Chemistry - HARYANA
Solutions
The Solutions chapter in Class 12 Chemistry explores homogeneous mixtures and their physical properties, specifically focusing on concentration terms, solubility, and colligative properties. For Haryana Board (BSEH) students, this is a high-scoring physical chemistry chapter that consistently appears in board exams. You will learn how solute-solvent interactions affect vapor pressure, boiling point, freezing point, and osmotic pressure through fundamental laws like Henry's Law and Raoult's Law. Mastering numerical problems based on molar mass determination using colligative properties and the Van 't Hoff factor is essential for securing top marks in your Class 12 board examinations.
Start Learning FreeKey Concepts
Molarity and Molality
Molarity is the number of moles of solute dissolved in one litre of solution, whereas molality is the number of moles of solute per kilogram of solvent. Molality is preferred over molarity for temperature-dependent calculations because mass does not change with temperature.
Henry's Law
It states that the partial pressure of a gas in vapor phase is proportional to the mole fraction of the gas in the solution. It explains why scuba divers experience bends and why soda bottles are sealed under high pressure.
Raoult's Law
For a solution of volatile liquids, the partial vapor pressure of each component of the solution is directly proportional to its mole fraction present in solution. It serves as the basis for distinguishing between ideal and non-ideal solutions.
Colligative Properties
Properties of solutions that depend only on the number of solute particles and not on their nature. These include relative lowering of vapor pressure, elevation of boiling point, depression of freezing point, and osmotic pressure.
Van 't Hoff Factor
It is the ratio of the normal molecular mass to the experimentally determined molecular mass, accounting for the extent of association or dissociation of solute particles in solution.
Important Formulas
Board Exam Info
In the Haryana Board (BSEH) Class 12 Chemistry examination, the Solutions chapter typically carries around 4 to 6 marks. Students can expect a mix of conceptual questions, short-answer questions defining laws like Henry's or Raoult's, and crucial numerical problems based on colligative properties and molar mass calculations.
Frequently Asked Questions
Why is molality preferred over molarity while expressing concentration of solutions?
Molality is preferred because it involves mass of the solvent, which does not change with a change in temperature, whereas molarity involves volume, which changes with temperature.
What is the difference between ideal and non-ideal solutions?
Ideal solutions obey Raoult's law over entire range of concentration and show zero enthalpy and volume change upon mixing. Non-ideal solutions deviate from Raoult's law and show either positive or negative deviations.
Why do colligative properties fail for solutes that undergo association or dissociation?
Because colligative properties depend on the total number of particles. Association or dissociation changes the actual number of particles in the solution, which is corrected using the Van 't Hoff factor (i).
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