Core Definitions (memorize exactly):

• Adsorption = surface phenomenon (adsorbate on adsorbent surface)
• Absorption = bulk phenomenon (substance penetrates into bulk)
• Colloid particle size = 1 nm to 1000 nm

Physisorption vs. Chemisorption (4 key differences):

1. Forces: van der Waals (P) vs. chemical bonds (C)
2. Enthalpy: 20–40 kJ/mol (P) vs. 80–240 kJ/mol (C)
3. Layers: multilayer (P) vs. monolayer (C)
4. Temperature: decreases with T (P) vs. first increases then decreases (C)

Freundlich Isotherm: \frac{x}{m} = $kP^{1/n}$ \qquad \left(0 < \frac{1}{n} < 1\right) $\log\frac{x}{m} = \log k + \frac{1}{n}\log P \quad \text{(slope = 1/n, intercept = log k)}$

Hardy-Schulze Rule:

• Higher valency of coagulating ion (opposite charge to sol) = greater coagulating power
• Negative sol ($As_{2}S_{3}$): $Al^{3+}$ > $Ba^{2+}$ > $Na^{+}$
• Positive sol (Fe(OH){3}): [Fe(CN){6}]^{4-} > $PO_{4}^{3-}$ > $SO_{4}^{2-}$ > $Cl^{-}$

Gold Number: Lower = Better Protection:

• Gelatin: 0.005 (BEST) < Albumin: 0.1 < Starch: 25 (WORST)

Colloids — 4 Key Properties:

1. Tyndall effect = light scattering
2. Brownian motion = zig-zag, due to molecular bombardment
3. Electrophoresis = migration in electric field (demonstrates charge)
4. Coagulation = charge neutralization → settling

Emulsions:

• O/W: milk, vanishing cream → mixes with water
• W/O: butter, cold cream → mixes with oil

Industrial Catalysts:

• Haber process: Fe catalyst ($N_{2}$ + $3H_{2}$ → $2NH_{3}$)
• Contact process: $V_{2}O_{5}$ catalyst ($2SO_{2}$ + $O_{2}$ → $2SO_{3}$)
• Selectivity: ZnO-$Cr_{2}O_{3}$ → $CH_{3}OH$; Cu → HCHO; Ni → $CH_{4}$ (from CO + $H_{2}$)

Enzyme Catalysis:

• Lock-and-key model (active site specific to substrate)
• Michaelis-Menten: v = Vmax[S]/(Km + [S]); Km = [S] at v = Vmax/2
• Competitive inhibitor: increases Km, Vmax unchanged
• Non-competitive inhibitor: Km unchanged, decreases Vmax