Class 12th Chemistry Solutions Notes

🌊 Introduction to Solutions 🌊

• A solution is a homogeneous mixture of two or more substances.
• The solute is the substance that is dissolved, and the solvent is the medium in which the solute dissolves.
• Solutions can be in the form of solid, liquid, or gas, depending on the phases of the solute and solvent.

🌟 Types of Solutions 🌟

1. Solid in Liquid:
   • Example: Salt in water or sugar in tea.
2. Liquid in Liquid:
   • Example: Alcohol in water or vinegar.
3. Gas in Liquid:
   • Example: Carbon dioxide in water (soda).
4. Solid in Solid:
   • Example: Alloys, like brass (copper and zinc).
5. Gas in Gas:
   • Example: Air, a mixture of oxygen, nitrogen, and other gases.

🔢 Concentration Terms 🔢

1. Molarity (M):
   • Defined as moles of solute per liter of solution.
   • Formula:

     M = \frac{\text{moles of solute}}{\text{volume of solution in liters}}

2. Molality (m):
   • Defined as moles of solute per kilogram of solvent.
   • Formula:

     m = \frac{\text{moles of solute}}{\text{mass of solvent in kg}}

3. Normality (N):
   • Defined as equivalents of solute per liter of solution.
   • It is often used in acid-base and redox reactions.
   • Formula:

     N = \frac{\text{equivalents of solute}}{\text{volume of solution in liters}}

🧪 Colligative Properties 🧪

• Colligative properties are properties that depend on the number of solute particles in a solution, not the nature of the solute.

1. Lowering of Vapour Pressure:
   • The vapor pressure of a solvent decreases when a non-volatile solute is dissolved in it.
   • The solution becomes less volatile compared to the pure solvent.
   • Raoult’s Law:

     P_{\text{solution}} = X_{\text{solvent}} \times P_{\text{solvent}}

2. Boiling Point Elevation:
   • The boiling point of a solution is higher than that of the pure solvent.
   • The increase in boiling point is directly proportional to the molality of the solution.
   • Formula:

     \Delta T_b = K_b \times m

3. Freezing Point Depression:
   • The freezing point of a solution is lower than that of the pure solvent.
   • The depression in freezing point is directly proportional to the molality of the solution.
   • Formula:

     \Delta T_f = K_f \times m

4. Osmotic Pressure:
   • Osmotic pressure is the pressure required to stop the flow of solvent into the solution through a semi-permeable membrane.
   • Formula:

     \Pi = i \times M \times R \times T

 - \Pi is the osmotic pressure,
 - i is the van’t Hoff factor (number of particles),
 - M is the molarity of the solution,
 - R is the gas constant,
 - T is the temperature in Kelvin.

🌈 Key Concepts to Remember 🌈

1. Solute and Solvent: Solute is dissolved in solvent to form a solution.
2. Types of Solutions: Solid in liquid, liquid in liquid, gas in liquid, and gas in gas.
3. Concentration Terms: Molarity, molality, and normality.
4. Colligative Properties: Lowering of vapor pressure, boiling point elevation, freezing point depression, and osmotic pressure.
5. Dependence on Number of Particles: Colligative properties depend on the number of solute particles, not their nature.