Previous Year Pattern Note

Pattern 1: Physisorption vs. Chemisorption Comparison (Most Frequent)

Question style: "Which of the following is TRUE/FALSE about physisorption/chemisorption?"
Most tested property: Temperature effect (1 question nearly every other year)
Key fact tested: Physisorption decreases with T; chemisorption first increases then decreases
Second most tested: Number of layers (physisorption = multilayer; chemisorption = monolayer)
Third: Enthalpy values (physisorption 20–40; chemisorption 80–240 kJ/mol)

Pattern 2: Hardy-Schulze Rule for Coagulation (High Frequency)

Question style: Given charged colloid + list of electrolytes → which has highest/lowest coagulating power?
Strategy: Identify sol charge → identify opposite-charged ion in each electrolyte → rank by valency
Common examples: $As_{2}S_{3}$ (negative) → $Al^{3+}$ > $Ba^{2+}$ > $Na^{+}$ ; Fe(OH){3} (positive) → [Fe(CN){6}]^{4-} > $SO_{4}^{2-}$ > $Cl^{-}$

Pattern 3: Gold Number and Protective Colloids (Medium Frequency)

Question style: Given gold numbers → rank by protective power; or define gold number
Key: Lower gold number = BETTER protective colloid = LESS mass needed
Memorize: Gelatin (0.005) < Albumin (0.1) < Starch (25)

Pattern 4: Colloidal Properties — Tyndall, Brownian Motion (Medium)

Question style: "What phenomenon explains [observation]?" — match phenomenon to observation
Tyndall effect = light scattering by colloid
Brownian motion = zig-zag movement due to molecular bombardment
Electrophoresis = migration in electric field → shows charge
Coagulation = neutralization of charge → settling

Pattern 5: Freundlich Isotherm Calculation (Low-Medium)

Pattern 6: Emulsion Type Identification (Low)