Written by Chapter 2 of Class 12 Chemistry, titled “Solutions,” focuses on understanding the various types of solutions and their properties. A solution is a homogeneous mixture of two or more substances, consisting of a solute dissolved in a solvent. This chapter explores different types of solutions based on the physical states of the solute and solvent, including solid, liquid, and gaseous solutions.
One of the key concepts discussed is the concentration of solutions, which can be expressed in various ways, such as molarity, molality, mole fraction, and percentage composition. Molarity (M) is defined as the number of moles of solute per liter of solution, while molality (m) is the number of moles of solute per kilogram of solvent. These concentration units are essential in calculating the composition of solutions in different scenarios.
The chapter also delves into the concept of solubility, which is the maximum amount of solute that can dissolve in a given quantity of solvent at a specific temperature. The solubility of gases in liquids is governed by Henry’s law, which states that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid.
Another important topic covered is the colligative properties of solutions, which are properties that depend on the number of solute particles rather than their nature. These include relative lowering of vapor pressure, elevation of boiling point, depression of freezing point, and osmotic pressure. The chapter explains how these properties are related to the molar mass of the solute and provides equations to calculate them.
In summary, Chapter 2 “Solutions” provides a comprehensive understanding of the formation, concentration, and properties of solutions, laying the foundation for further studies in physical chemistry.
Class 12th Chemistry Chapter 2 Solution Book 📚 PDF Download
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Question & answer
Define molarity. How is it calculated?
Answer:Molarity (M) is defined as the number of moles of solute present in 1 liter of solution
Explain Raoult’s law for a solution of volatile liquids.
Answer:Raoult’s law states that the partial vapor pressure of each volatile component in a solution is directly proportional to its mole fraction in the solution.
What is the Van’t Hoff factor (i)? How does it affect colligative properties?
Answer:The Van’t Hoff factor (i) is the ratio of the actual number of particles in solution after dissociation to the number of formula units initially dissolved. It affects colligative properties like boiling point elevation and freezing point depression by multiplying the expected effect by the factor i.
Differentiate between ideal and non-ideal solutions.
Answer:Ideal Solutions: Obey Raoult’s law at all concentrations. No heat change and volume change upon mixing.
Non-Ideal Solutions: Do not obey Raoult’s law. May show positive or negative deviation, with associated enthalpy changes.
What are colligative properties? Name four.
Answer:Colligative properties depend on the number of solute particles in the solution, not on their nature.
Examples :Relative lowering of vapor pressure ,Boiling point elevation, Freezing point depression, Osmotic pressure
Explain Henry’s law and its application.
Answer: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 liquid.
What is an azeotropic mixture? Give an example
Answer:An azeotropic mixture is a mixture of two or more liquids that form a constant boiling liquid of distinct composition. Example: Ethanol and water form an azeotrope with 95% ethanol and 5% water.
Explain the concept of relative lowering of vapor pressure.
Answer:Relative lowering of vapor pressure is the ratio of the decrease in vapor pressure of the solvent upon adding a non-volatile solute to the original vapor pressure of the pure solvent.
What are the deviations from Raoult’s law?
Answer:Positive deviation: The observed vapor pressure is higher than predicted, due to weaker intermolecular forces.
Negative deviation: The observed vapor pressure is lower than predicted, due to stronger intermolecular forces.
Discuss the factors affecting solubility of gases in liquids.
Answer:Factors include
Pressure: According to Henry’s law, solubility increases with pressure.
Temperature: Solubility decreases with an increase in temperature.
Nature of the gas: More soluble gases like ( CO_2 ) have stronger interactions with the solvent.
Explain the term ideal solution with an example.
Answer:An ideal solution is one where the intermolecular interactions between the components are the same as in the pure components.
Example: Benzene and toluene.
What are the applications of osmotic pressure in real life?
Answer:Osmotic pressure is used in reverse osmosis for water purification, in food preservation by creating hypertonic conditions, and in medicine for administering intravenous fluids.
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