Solutions
Learn Solutions with notes, examples, and practice questions.
Chapter Overview
Colligative properties depend on number of solute particles, not their identity — ideal for determining molar mass.
Solutions are homogeneous mixtures. Concentration terms (molarity, molality, mole fraction), solubility, Raoult's law, and colligative properties link chemistry to measurable physical changes.
Concentration
Molarity
M = moles solute / L solution
Molality
m = moles solute / kg solvent
Mole fraction
X_A = n_A / (n_A + n_B)
Mass %
(mass solute / mass solution) × 100
Raoult's Law
Vapour pressure
P_A = X_A · P°_A
Ideal solution
Obey Raoult's law at all concentrations
Non-ideal
Positive/negative deviation from Raoult's law
Colligative Properties
ΔT_b
ΔT_b = K_b m
ΔT_f
ΔT_f = K_f m
Osmotic π
π = MRT
van't Hoff
i = observed particles / formula units
Solved Examples
Step-by-step solutions — read each step before checking the final answer.
Molarity
0.5 mol in 2 L.
- 1M=0.5/2=0.25 M
Answer
0.25 M
Boiling point elevation
m=1, K_b=0.52 K·kg/mol.
- 1ΔT_b=0.52 K
Answer
Boiling point rises 0.52 K
Key Points to Remember
- ✓ Dilution: M₁V₁=M₂V₂
- ✓ i for electrolytes > 1
- ✓ Hypertonic/hypotonic/isotonic in biology link
Exam Tips
- • Watch units: L vs mL, kg solvent vs kg solution
- • Use i in colligative when solute dissociates
Formula Cheat Sheet
Quick reference — NCERT board exam formulas
Concentration Terms
- Molarity:M = moles solute / L solution
- Molality:m = moles solute / kg solvent
- Mole fraction:X_A = n_A / (n_A + n_B)
- Mass %:(mass solute / mass solution) × 100
- Dilution:M₁V₁ = M₂V₂
Raoult's Law & Colligative Properties
- Vapour pressure:P_A = X_A · P°_A
- Boiling elevation:ΔT_b = K_b m
- Freezing depression:ΔT_f = K_f m
- Osmotic pressure:π = MRT
- van't Hoff factor:i = observed particles / formula units
Practice MCQs — Solutions
Test your understanding with topic-wise multiple choice questions. Explanations appear after each answer.
Molarity unit: