Chemistry Part I - Class XII Complete Comprehensive XII Study Guide

Types of Solutions
- Solutions are homogeneous mixtures of two or more components.
- Binary solutions consist of two components: Solvent (component in largest quantity) and Solute.
- Gaseous solutions: Air (Gas in Gas), Chloroform in Nitrogen (Liquid in Gas).
- Liquid solutions: Glucose in Water (Solid in Liquid), Ethanol in Water (Liquid in Liquid), Oxygen in Water (Gas in Liquid).
- Solid solutions: Alloys like Gold and Copper (Solid in Solid), Solution of hydrogen in palladium (Gas in Solid).
Expressing Concentration
- Mass percentage ( $w/w$ ):
 $\text{Mass } \% \text{ of component} = \frac{\text{Mass of component in solution}}{\text{Total mass of solution}} \times 100$
- Volume percentage ( $v/v$ ):
 $\text{Volume } \% \text{ of component} = \frac{\text{Volume of component}}{\text{Total volume of solution}} \times 100$
- Molarity ( $M$ ):
 $M = \frac{\text{Moles of solute}}{\text{Volume of solution in } dm^3}$
- Molality ( $m$ ):
 $m = \frac{\text{Moles of solute}}{\text{Mass of solvent in kg}}$
- Mole Fraction ( $x$ ):
 $xi = \frac{ni}{\sum n_j}$ (Sum of all mole fractions is 1).
- Parts per million ( $ppm$ ): Used for very dilute solute concentrations.
Solubility
- Max amount of solute that can be dissolved in a specific amount of solvent at a given temperature.
- Solubility of Liquid in Liquid/Solid in Liquid: Follows "like dissolves like" (Polar solutes in polar solvents).
- Solubility of Gas in Liquid: Increases with pressure.
- Henry's Law: The partial pressure of the gas in vapor phase ( $p$ ) is proportional to the mole fraction of the gas ( $x$ ) in the solution: $p = K_H x$ .
- Higher $K_H$ means lower solubility at a given pressure.
- Solubility of gases decreases with increase in temperature.
Vapor Pressure and Raoult's Law
- Raoult's Law: In a solution of volatile liquids, the partial vapor pressure of each component is directly proportional to its mole fraction: $pi = pi^0 x_i$ .
- Total pressure $P{total} = p1^0 x1 + p2^0 x_2$ .
- Ideal Solutions: Obey Raoult’s law over the entire concentration range. $\Delta H{mix} = 0$ and $\Delta V{mix} = 0$ .
- Non-Ideal Solutions: Show deviations from Raoult's law.
- Positive deviation: $A-B$ interactions weaker than $A-A$ or $B-B$ .
- Negative deviation: $A-B$ interactions stronger than $A-A$ or $B-B$ .
- Azeotropes: Binary mixtures having the same composition in liquid and vapor phase and boil at a constant temperature.
Colligative Properties
- Properties that depend only on the number of solute particles, not their nature.
- Relative Lowering of Vapor Pressure:
 $\frac{p1^0 - p1}{p1^0} = x2 \approx \frac{w2 \times M1}{M2 \times w1}$
- Elevation of Boiling Point:
 $\Delta Tb = Tb - Tb^0 = Kb m$
- Depression of Freezing Point:
 $\Delta Tf = Tf^0 - Tf = Kf m$
- Osmotic Pressure:
 $\pi = CRT = \frac{n_2}{V} RT$
- Van't Hoff Factor ( $i$ )
- Accounts for association or dissociation of solute.
- $i = \frac{\text{Normal molar mass}}{\text{Abnormal molar mass}} = \frac{\text{Observed colligative property}}{\text{Calculated colligative property}}$
- Updated formulas: $\Delta Tb = i Kb m$ , $\pi = i CRT$ .