1. Concentration Terms
A. Molarity (M)
Definition: Number of moles of solute present in 1 litre of solution.
Formula:
Where:
� = Mass of solute (g)
� = Molar mass of solute
� = Volume of solution (mL)
Important: Molarity changes with temperature because volume changes.
B. Molality (m)
Definition: Number of moles of solute present in 1 kg of solvent.
Formula:
Where:
� = Mass of solvent (g)
Important: Molality is independent of temperature.
⭐ Frequently asked theory question.
C. Mole Fraction (x)
Key Relation:
2. Solubility & Vapour Pressure
A. Henry's Law
Statement: The solubility of a gas in a liquid is directly proportional to its pressure.
Where:
� = Solubility
� = Henry's constant
� = Pressure
B. Raoult's Law
For a solution containing two volatile liquids:
Where:
�, � = Vapour pressures of pure liquids
�, � = Mole fractions
C. Ideal vs Non-Ideal Solutions
Ideal Solution
Non-Ideal Solution
Follows Raoult's law completely
Deviates from Raoult's law
ΔV = 0
ΔV ≠ 0
ΔH = 0
ΔH ≠ 0
Example: Benzene + Toluene
Shows positive/negative deviation
3. Colligative Properties
Definition
Properties that depend only on the number of solute particles, not on their nature.
A. Relative Lowering of Vapour Pressure (RLVP)
For dilute solutions:
Where:
� = Vapour pressure of pure solvent
� = Vapour pressure of solution
B. Elevation of Boiling Point
Where:
� = Ebullioscopic constant
C. Depression of Freezing Point
Where:
� = Cryoscopic constant
D. Osmotic Pressure
Where:
� = Molarity
� = 0.0821 L atm K⁻¹ mol⁻¹
� = Temperature in Kelvin
Expanded form:
4. Van't Hoff Factor (i) ★ Most Important
When solute particles dissociate or associate, the number of particles changes.
Formula
Non-Electrolytes
Do not dissociate.
Examples:
Urea
Glucose
Sucrose
Strong Electrolytes
NaCl
MgCl₂
Al₂(SO₄)₃
Degree of Dissociation (α)
Where:
� = Total ions formed
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