Chemistry Class 12 Solutions: Types, Colligative Properties, and Solubility

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12 Questions

What defines an ionic solution?

Homogeneous mixture of salts dissolved in a polar solvent

Why do covalent solutions not conduct electricity?

Because they lack free charges for electrical conduction

What are colligative properties dependent on?

The number of solute particles present

Which example best represents a covalent solution?

Sugar (C₁₂H₀₂O₁₁) dissolving in water (H₂O)

In which type of mixture do ions hold the solution together via electrostatic forces?

Ionic solutions

Why do colligative properties only depend on the number of solute particles?

To ensure consistency across different types of solutes

What property refers to the force required to prevent a solvent from flowing through a semipermeable membrane towards a concentrated solution?

Osmotic pressure

Which colligative property increases with increasing molarity of the solute?

Osmotic pressure

What property involves a higher temperature requirement for a solvent to reach its boiling point in a solution state?

Boiling point elevation

Which factor plays a crucial role in determining solubility based on polarity or polarity difference between the solvent and solute?

Nature of the substances

What is the effect of heating on solubility?

Increases solubility

How does the addition of a volatile solute affect the total vapor pressure of a system?

Decreases vapor pressure

Study Notes

Chemistry Class 12 Solutions: A Deeper Dive into Liquid Mixtures

In our study of chemistry, solutions form a fundamental concept, especially when we delve deeper into Class 12 curriculum. In this context, let's explore three critical aspects of solutions—types, colligative properties, and solubility.

Types of Solutions

A solution is a homogeneous mixture containing one or more solutes dissolved in a solvent. We can classify them based on their components:

  • Ionic Solutions: Form when ionic compounds like salts dissolve in water (polar solvent) to produce electrically charged particles called ions, which work together to hold the solution together via electrostatic forces. Examples: Sodium chloride (NaCl), Magnesium sulfate (MgSO₄), Calcium nitrate (Ca(NO₃)₂).
  • Covalent Solutions: Occur when nonmetal elements or molecular compounds dissolve in another substance, often polar covalent or nonpolar liquids. Unlike ionic solutions, these mixtures do not conduct electricity because they lack free charges. Examples: Sugar (C₁₂H₀₂O₁₁) dissolving in water (H₂O), Carbon dioxide (CO₂) dissolving in liquid ammonia (NH₃).

Colligative Properties

Colligative properties are unique characteristics exhibited by dilute solutions and depend only upon the number of solute particles present, regardless of the type of solute involved. These properties arise due to increased concentration of solute particles leading to osmotic pressure, lower boiling points, higher vapor pressures, and depression of freezing points. Some important colligative properties include:

  • Osmotic Pressure: This property refers to the force required to prevent a solvent from flowing through a semipermeable membrane towards a concentrated solution. It increases with increasing molarity of the solute.
  • Boiling Point Elevation: When a pure solvent changes to its solution state, it requires a higher temperature to reach its boiling point. For example, consider sugar in water; as the concentration of sugar rises, the boiling point also rises.
  • Freezing Point Depression: As the concentration of a solute increases in a solution, the freezing point decreases. Conversely, an increase in temperature is needed to maintain a constant melting point.
  • Vapour Pressure Lowering: When a volatile solute is added to a solvent, the total vapour pressure of the system will decrease. An indicator of this phenomenon is Raoult’s Law, which states that the partial pressure exerted by each component in a mixture is directly proportional to its mole fraction in the mixture.


Solubility refers to the extent to which a solute dissolves in a given amount of solvent at a specific temperature and pressure. Various factors influence whether two substances mix readily or sparingly:

  • Temperature: Heating usually leads to an enhanced capacity of a solvent to dissolve a solute, while cooling may lead to reduced solubility of both gaseous and solid solutes.
  • Nature of the Substances: Polarity or polarity difference between the solvent and solute plays a crucial role in determining solubility, as does the presence of strong intermolecular forces such as hydrogen bonding, van der Waals forces, etc..
  • Pressure: Under high pressure, certain gases become increasingly soluble in liquids. However, this effect is less significant compared to those of other factors.

Understanding these concepts in detail helps us comprehend the behavior of different types of solutions, how solutions exhibit unexpected behaviors due to colligative properties, and why some substances dissolve easily under particular conditions, while others don't. Armed with this knowledge, you'll find yourself well-equipped to tackle more advanced topics in physical chemistry and chemical engineering!

Dive into the depths of liquid mixtures in Chemistry Class 12 as we explore the types of solutions (ionic and covalent), colligative properties (osmotic pressure, boiling point elevation, freezing point depression, vapor pressure lowering), and factors affecting solubility.

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