From milk to clouds to catalytic converters — the chemistry of interfaces. With interactive adsorption isotherm plotter, colloid diagrams, and 20+ real-life examples.
Before diving in, here's the entire chapter on one page. From adsorption → catalysis → colloids → emulsions and their applications.
Surface chemistry studies phenomena at interfaces. Adsorption = accumulation of molecules on a surface (physisorption: weak forces; chemisorption: covalent bonds). Isotherms (Freundlich, Langmuir) quantify adsorption. Catalysis speeds reactions via surface adsorption. Colloids = particles 1-1000 nm dispersed in a medium. Lyophilic vs lyophobic, aerosols, foams, emulsions, gels. Tyndall effect, Brownian motion, electrophoresis characterize colloids.
Adsorption: The accumulation of molecules (or ions) of a substance at the surface of a solid or liquid, rather than in the bulk.
Adsorbent: The substance on whose surface adsorption occurs (usually solid). Example: activated charcoal, silica gel.
Adsorbate: The substance that gets adsorbed (usually gas or solute). Example: N₂ gas on charcoal.
Desorption: Removal of adsorbed molecules (reverse of adsorption).
Absorption: Molecules penetrate the bulk of the material (not just surface). Example: water absorbed by sponge.
| Feature | Physisorption | Chemisorption |
|---|---|---|
| Force | Van der Waals (weak) | Covalent bonds (strong) |
| Enthalpy | Low (−20 kJ/mol) | High (−200 kJ/mol) |
| Specificity | Non-specific | Highly specific |
| Reversibility | Reversible (desorption easy) | Usually irreversible |
| Temperature | Favored at low T | Favored at high T (activation energy) |
| Multilayer | Forms multilayers | Forms monolayer only |
| Example | H₂ on charcoal | O₂ on iron (rusting) |
Adsorption = accumulation at surface. Physisorption (weak, non-specific, reversible) vs chemisorption (strong, specific, often irreversible). Factors: surface area, T, P, nature. Applications: charcoal, gas masks, chromatography, catalysis.
Adsorption isotherm: A graph showing the amount of adsorbate adsorbed (x) per unit mass of adsorbent (m) vs pressure of gas (p) at constant temperature.
Plot: x/m (y-axis) vs p (x-axis)
At low p: Linear increase (Henry's Law region)
At high p: Plateau (saturation — all sites occupied)
Empirical equation: x/m = k·p^(1/n)
Where: x = mass of adsorbate, m = mass of adsorbent, p = pressure, k and n = constants (n > 1)
Logarithmic form: log(x/m) = log k + (1/n)·log p
Graph: log(x/m) vs log p → straight line
Limitation: Valid only up to moderate pressure. Fails at high pressure (saturation).
Theoretical model: Assumes monolayer adsorption on specific sites with equal energy. No interaction between adsorbed molecules.
Equation: x/m = (a·p) / (1 + b·p)
Rearranged: p/(x/m) = 1/a + (b/a)·p
Graph: p/(x/m) vs p → straight line
At low p: x/m ∝ p (Henry's region)
At high p: x/m → a/b (saturation, constant)
Enter Freundlich parameters (k, 1/n) — see how adsorption varies with pressure.
Freundlich: x/m = k·p^(1/n), empirical (log-log linear). Langmuir: theoretical, monolayer, gives saturation at high p. Both describe adsorption data; Freundlich fails at high p, Langmuir assumes ideal surface.
Catalyst: Substance that increases rate of a reaction without being consumed. Provides alternate pathway with lower activation energy.
Types of catalysis:
1. Homogeneous catalysis: Catalyst and reactants in same phase
2. Heterogeneous catalysis: Catalyst and reactants in different phases
Steps:
Active sites: Specific locations on the catalyst surface (edges, corners, defects) where adsorption is strongest. Number of active sites determines catalyst activity.
Zeolites: Aluminosilicate minerals with porous structure — used as molecular sieves.
Only molecules of a certain size can enter the pores and react (shape-selective). Example: ZSM-5 converts methanol to gasoline-range hydrocarbons selectively.
Catalysis: homogeneous (same phase) or heterogeneous (different phases, solid catalyst). Mechanism: adsorption on active sites → reaction → desorption. Properties: activity, selectivity. Promoters increase, poisons decrease activity. Zeolites are shape-selective. Key industrial applications: NH₃, H₂SO₄, catalytic converters, oil hydrogenation.
Colloid: A heterogeneous mixture where particles of one substance (dispersed phase) are distributed in another (dispersion medium). Particle size: 1 nm – 1000 nm (1 μm).
Dispersed phase: The substance that is dispersed (e.g., particles in milk).
Dispersion medium: The substance in which dispersion happens (e.g., water in milk).
Compare:
| Dispersed | Dispersion | Name | Example |
|---|---|---|---|
| Solid | Liquid | Sol | Paint, ink, milk of magnesia |
| Solid | Gas | Aerosol (solid) | Smoke, dust |
| Solid | Solid | Solid sol | Ruby glass, some alloys |
| Liquid | Liquid | Emulsion | Milk, mayonnaise |
| Liquid | Gas | Aerosol (liquid) | Fog, mist, clouds |
| Liquid | Solid | Gel | Jelly, cheese, butter |
| Gas | Liquid | Foam | Whipped cream, shaving cream |
| Gas | Solid | Solid foam | Pumice, styrofoam |
| Feature | Lyophilic | Lyophobic |
|---|---|---|
| Affinity for medium | High (love solvent) | Low (hate solvent) |
| Ease of formation | Easy (spontaneous) | Requires special methods |
| Stability | Very stable (self-stabilizing) | Unstable (need stabilizer) |
| Reversibility | Reversible (solvent + solid reconstitutes) | Irreversible |
| Viscosity | Higher than medium | Similar to medium |
| Example | Starch in water, protein in water | Gold sol, As₂S₃ sol, Fe(OH)₃ sol |
Hydrosol: Lyophilic colloid with water as medium (gelatin in water).
Alcosol: Lyophilic colloid with alcohol as medium.
Aerosol: Dispersion of liquid/solid in gas.
Macromolecular colloids: Large molecules (proteins, polymers) form colloids by themselves — their size is already in the colloidal range. Example: starch, protein, cellulose, nylon.
Associated colloids (micelles): Small molecules that aggregate to form colloidal particles at higher concentration. Example: soap, detergents.
Critical Micelle Concentration (CMC): The minimum concentration above which micelles form. Below CMC, molecules are individual; above CMC, they aggregate into micelles (50-100 molecules).
Kraft temperature: The temperature above which micelle formation happens for soap. Below this, soap doesn't form micelles (doesn't clean).
Colloids = particles 1-1000 nm. 8 types by phase state (sol, gel, emulsion, foam, aerosol). Lyophilic (love solvent, stable) vs lyophobic (hate solvent, unstable). Macromolecular colloids (large molecules). Associated colloids (micelles at CMC). Soap = micelle former.
1. Chemical methods: Chemical reactions that produce colloidal-sized particles.
2. Electrical (Bredig's arc) method: For metal sols. Electric arc between metal electrodes in water → metal vaporizes → condenses as colloid. Used for Au, Pt, Ag sols.
3. Peptization: Converting a precipitate into a colloid by adding electrolyte. Example: Fe(OH)₃ precipitate + small amount of FeCl₃ → Fe(OH)₃ sol. The electrolyte (peptizing agent) provides ions that adsorb on particles, giving them charge and dispersing them.
4. Physical methods:
1. Dialysis: Uses a semipermeable membrane (like cellophane) — small ions/molecules pass through, colloidal particles are retained. Removes excess electrolytes.
2. Electrodialysis: Dialysis + electric field — faster removal of ions. Ions migrate to electrodes.
3. Ultrafiltration: Filtration through fine pores (collodion membrane) — small molecules pass, colloid particles are retained. Can be used to concentrate colloids.
4. Ultracentrifugation: High-speed spinning separates colloid particles from solution based on density. Used to determine particle size distribution.
Preparation: chemical (double decomposition, reduction, hydrolysis), electrical (Bredig's arc), peptization (precipitate + electrolyte → colloid), physical (ultrasonic, mechanical). Purification: dialysis (semipermeable membrane), electrodialysis, ultrafiltration, ultracentrifugation. Used in medicine (artificial kidney), food (dairy), materials.
Colloids have very low particle concentration (compared to true solutions), so colligative properties are much smaller. But they can still be measured and used to determine particle size.
Tyndall effect: Scattering of light by colloidal particles. The path of light becomes visible when passing through a colloid (like sunbeams through fog).
Cause: Colloidal particles (1-1000 nm) are similar in size to the wavelength of visible light — they scatter light (Rayleigh scattering). Larger particles scatter more (longer wavelength light), smaller particles scatter less (blue light).
Uses:
Brownian motion: Random, zig-zag motion of colloidal particles suspended in a medium. Caused by unbalanced collisions of medium molecules on the particle.
Importance:
Colloidal particles carry charge (positive or negative) due to adsorption of ions or ionization of surface groups.
Electrophoresis: Movement of colloidal particles under an applied electric field. Positive particles move toward cathode; negative particles move toward anode.
Electrical double layer: Two layers of charge at the surface — a fixed layer (adsorbed ions) and a diffuse layer (balancing ions in solution).
Coagulation: Aggregation of colloidal particles (destabilization). Caused by:
Hardy-Schulze rule: Coagulating power of an ion ∝ charge^n (n = 1 for oppositely charged ions). Higher charge → more effective coagulator. Al³⁺ > Ca²⁺ > Na⁺ for negative sols.
Colloid properties: Tyndall (light scattering), Brownian (random motion), electrophoresis (charged particles move in field), coagulation (aggregation). Hardy-Schulze rule: higher charge = more effective coagulator. Applications: water purification, DNA analysis, paint deposition.
Emulsion: A colloidal system where both dispersed phase and dispersion medium are liquids (immiscible).
Types:
Emulsifier (emulsifying agent): Substance that stabilizes an emulsion by preventing the droplets from coalescing. Forms a film at the interface between the two liquids.
Examples:
Mechanism: Emulsifier molecules have both hydrophilic (water-loving) and hydrophobic (water-fearing) parts. They arrange at the oil-water interface, preventing droplets from merging.
Breaking an emulsion to separate the two liquids. Methods:
Example: Creaming of milk (fat rises when left to stand), separation of cream from milk by centrifugation.
Emulsions = liquid-in-liquid colloids. O/W (oil in water) or W/O (water in oil). Emulsifiers (soap, proteins, lecithin) stabilize by forming a film at interface. Demulsification (breaking) by heat, electrolyte, centrifugation. Common in food, cosmetics, pharmaceuticals.
1. Analytical chemistry:
2. Catalysis:
3. Water purification:
4. Medicine:
5. Food and cosmetics:
6. Environment:
7. Materials science:
8. Photography:
9. Lubrication:
10. Miscellaneous:
Activated charcoal has an incredibly high surface area — 1 gram can have surface area up to 3,000 m² (roughly the size of a football field)! This is why it's so effective at adsorbing toxins and impurities. It's used in water filters, gas masks, poison treatment, and even for deodorizing refrigerators.
Surface chemistry has widespread applications: analytical (chromatography, electrophoresis), catalysis (industrial, environmental), water purification, medicine (dialysis, drug delivery), food and cosmetics (emulsions, foams, gels), environment (adsorption, photocatalytic degradation), materials (nanoparticles, thin films), photography, lubrication. Understanding interfaces is fundamental to modern technology.
"Adsorption = A on Surface" (surface accumulation)
"Absorption = A through Body" (into bulk)
"Physisorption is PHysical = PHriendly" (weak, reversible)
"Chemisorption is CHEMical = CHEmical bonds" (strong, often irreversible)
"x/m = k·p^(1/n)"
Say "x over m equals k p to the one over n"
Log form: log(x/m) = log k + (1/n) log p
"Monolayer, no interaction"
x/m = ap/(1 + bp) → p/(x/m) = 1/a + (b/a)p
"Philic = PHriends (love solvent)"
"Phobic = Fearing (hate solvent)"
Lyophilic = stable, reversible. Lyophobic = unstable, irreversible.
"TYNDALL = THe light is visible"
Scattering of light by colloid particles. Sunbeams through fog, headlights in fog.
"HIgher Charge = Higher Coagulating power"
Al³⁺ > Ca²⁺ > Na⁺ for coagulating negative sols. Used in water purification.
"O/W = Oil in Water (milk, mayo)"
"W/O = Water in Oil (butter, cream)"
"SLG-S" — Solid in Liquid = Sol; Liquid in Gas = Aerosol; Gas in Liquid = Foam; Solid in Solid = Solid sol.
"CMC = Critical Micelle Concentration" — above this, micelles form
"Kraft = Above this temp, soap works"
Use "Adsorption = A on Surface" for surface vs bulk, "Physisorption = PHriendly" for weak forces, "TYNDALL = THe light is visible" for scattering, "Hardy-Schulze = Higher Charge = Higher Coagulation".
Q1. Why is adsorption exothermic?
When molecules adsorb on a surface, they lose some degrees of freedom (become more ordered). The surface energy decreases. This energy is released as heat → exothermic.
Adsorption: Gas + Solid surface → Gas·surface + heat (ΔH < 0)
Physical adsorption (physisorption): ΔH ~ −20 kJ/mol (Van der Waals).
Chemical adsorption (chemisorption): ΔH ~ −200 kJ/mol (bonds form).
Q2. What is the Tyndall effect? Give two applications.
Tyndall effect = scattering of light by colloidal particles. The path of a beam of light becomes visible when it passes through a colloid (because particles of 1-1000 nm scatter light).
Colloidal particle size is comparable to the wavelength of visible light (~400-700 nm). Light scatters (Rayleigh scattering) when it hits these particles. Larger particles scatter more. True solutions (particle size < 1 nm) don't scatter → no Tyndall.
(1) Distinguishes colloids from true solutions — a beam of light is visible through colloid but not through true solution.
(2) Explains the blue color of sky (sunlight scattered by atmospheric aerosol particles and gas molecules).
(3) Explains visibility of headlights in fog (liquid droplets in air — aerosol).
(4) Used in ultramicroscopes to detect individual colloidal particles.
Q3. What is the Hardy-Schulze rule? Explain with an example.
Hardy-Schulze rule states that the coagulating power of an ion is directly proportional to the charge of the ion (or more precisely, to some power of its charge), when the ion has charge opposite to that of the colloidal particle.
For a negatively charged colloid (e.g., As₂S₃ sol, Au sol), positive ions (cations) cause coagulation. Higher charge = more effective:
Al³⁺ > Ca²⁺ > Na⁺ > H⁺
For a positively charged colloid (e.g., Fe(OH)₃ sol), anions coagulate:
[Fe(CN)₆]³⁻ > SO₄²⁻ > Cl⁻
In water purification, alum (Al₂(SO₄)₃) is used as coagulant. The Al³⁺ ions (high charge) coagulate the negatively charged colloidal impurities. NaCl would be much less effective. This is why alum is used — very effective at removing turbidity from water.
Q4. Distinguish between physisorption and chemisorption. What are the factors that affect adsorption?
Weak Van der Waals forces. Low enthalpy (−20 kJ/mol). Non-specific. Reversible. Multilayer possible. Favored at low T. Example: N₂ on charcoal.
Covalent bonds. High enthalpy (−200 kJ/mol). Highly specific. Often irreversible. Monolayer only. Favored at high T (needs activation). Example: H₂ on Ni.
Greater surface area → more adsorption (activated charcoal, finely divided metals). This is why catalysts are porous.
Physisorption decreases with increasing T (exothermic, Le Chatelier). Chemisorption increases initially (needs activation) then decreases. Optimal T for maximum adsorption.
Nature of adsorbent: porous, high-surface-area materials. Nature of adsorbate: easily liquefiable gases (CO₂, SO₂) adsorb more than non-liquefiable (H₂, N₂). Pressure: higher pressure → more adsorption (for gases).
Q5. Discuss the classification of colloids based on the physical state of dispersed phase and dispersion medium. Give examples.
Colloid = heterogeneous system with particle size 1-1000 nm. Dispersed phase + dispersion medium. Both can be solid, liquid, or gas (but not both gas).
| Dispersed | Dispersion | Name | Example |
|---|---|---|---|
| Solid | Liquid | Sol | Paint, milk of magnesia |
| Solid | Gas | Aerosol (solid) | Smoke, dust |
| Solid | Solid | Solid sol | Ruby glass, alloys |
| Liquid | Liquid | Emulsion | Milk, mayonnaise |
| Liquid | Gas | Aerosol (liquid) | Fog, mist |
| Liquid | Solid | Gel | Jelly, butter, cheese |
| Gas | Liquid | Foam | Whipped cream, shaving cream |
| Gas | Solid | Solid foam | Pumice, styrofoam |
Gas-in-gas (like air) is a true solution, not a colloid — gas molecules are too small. All other 8 combinations can form colloids.
Q6. What is an emulsion? Discuss the role of emulsifying agents with examples.
Emulsion = liquid-in-liquid colloid of two immiscible liquids. Types: O/W (oil in water) and W/O (water in oil).
Examples: Milk, mayonnaise (O/W). Butter, cold cream (W/O).
Emulsifier = substance that stabilizes emulsion by forming a film at the interface between the two liquids.
Mechanism: Emulsifier molecules have both hydrophilic (polar, water-loving) and hydrophobic (non-polar, water-fearing) parts. They align at the interface — hydrophilic part in water, hydrophobic part in oil. This creates a physical barrier preventing droplets from coalescing.
Examples: soap (for O/W), lecithin in egg yolk, casein in milk, gum arabic, proteins, long-chain alcohols (for W/O).
Whether an emulsion is O/W or W/O depends on the emulsifier and the volume ratio of the two liquids.
Example: Milk is O/W because casein (protein) is more soluble in water (hydrophilic). Butter is W/O because churning removes the water phase, leaving fat droplets with some water inside.
Breaking the emulsion (separation): heating, adding electrolyte, centrifugation, adding demulsifier, freezing.
Example: Creaming of milk (fat rises), separation of cream by centrifugation.
Selected exercise questions from the LEGACY NCERT Chapter 5 (Surface Chemistry). Removed from current syllabus but useful for competitive exams.
Adsorption: Accumulation of molecules at the surface of a solid or liquid. The adsorbate stays on the surface, not inside.
Example: H₂ gas adsorbed on the surface of activated charcoal (H₂ sticks to surface, doesn't enter).
Absorption: Molecules penetrate the bulk of the material (go inside).
Example: Water absorbed by a sponge (water goes throughout the sponge).
Key difference: Adsorption is surface phenomenon; absorption is bulk phenomenon. (Sorption = both together.)
Answer: Adsorption occurs at the surface. Finely divided substances have much greater surface area per unit mass compared to bulk materials.
For example: 1 g of finely divided activated charcoal has surface area up to 3000 m², while 1 g of charcoal chunk has only a few cm².
Greater surface area = more adsorption sites = more adsorption = more effective adsorbent.
This is why industrial adsorbents are highly porous (silica gel, activated charcoal, zeolites).
Factors:
(1) Surface area: Higher surface area → more adsorption (porous adsorbents are better).
(2) Temperature: Adsorption is exothermic. Physisorption decreases with T. Chemisorption may increase (if activation needed) then decrease.
(3) Pressure: Higher pressure → more gas adsorption (at constant T).
(4) Nature of adsorbent: Porous, high surface area → more adsorption. Chemically active surfaces adsorb more.
(5) Nature of adsorbate: Easily liquefiable gases (CO₂, SO₂, NH₃) adsorb more than non-liquefiable (H₂, N₂, O₂) — because attractive forces are stronger for larger, more polarizable molecules.
Physisorption:
• Weak Van der Waals forces
• Low enthalpy of adsorption (ΔH ≈ −20 kJ/mol)
• Non-specific
• Reversible
• Multilayer formation
• Favored at low T
• Example: N₂ on charcoal, H₂ on charcoal
Chemisorption:
• Covalent bond (or ionic) formation
• High enthalpy (ΔH ≈ −200 kJ/mol)
• Highly specific
• Usually irreversible
• Monolayer only
• Favored at high T (needs activation energy)
• Example: H₂ on Ni (hydrogenation catalyst), O₂ on Fe (rusting)
Zeolites: Aluminosilicate minerals with a 3D porous structure (microporous, pore size 0.3–1 nm). They are used as molecular sieves and shape-selective catalysts.
Features:
(1) Shape-selective: The pores have a specific size and shape, so only molecules that fit can enter and react. This gives high selectivity.
(2) High surface area: Large internal surface area for adsorption.
(3) Ion-exchange ability: Can exchange cations (like Na⁺ for H⁺) to modify acidity and catalytic properties.
(4) Thermally stable: Withstand high temperatures used in refinery processes.
(5) Examples: ZSM-5 (converts methanol to gasoline-range hydrocarbons), zeolite Y (cracking of petroleum).
Colloid: A heterogeneous system in which particles of one substance (dispersed phase, 1-1000 nm in size) are distributed throughout another substance (dispersion medium). The particles are larger than molecules but smaller than those in suspensions. Colloids appear homogeneous but are actually heterogeneous.
Types by phase: 8 types (see table). Examples: sol (solid in liquid), gel (liquid in solid), emulsion (liquid in liquid), foam (gas in liquid), aerosol (solid/liquid in gas).
Types by affinity: Lyophilic (love solvent, stable) and lyophobic (hate solvent, unstable).
Types by size: Macromolecular (large molecules) and associated (micelles).
(a) Tyndall effect: Scattering of light by colloidal particles. When a beam of light passes through a colloid, the path becomes visible because the particles scatter the light in all directions. This distinguishes colloids from true solutions (which don't scatter). The blue color of the sky and headlights visible in fog are examples.
(b) Brownian motion: Random, zigzag movement of colloidal particles suspended in a medium. Caused by unbalanced collisions of the medium's molecules on the particles. Provides kinetic stability (prevents settling) and confirms kinetic theory of matter. Named after botanist Robert Brown.
(c) Electrophoresis: Movement of charged colloidal particles under an applied electric field. Positively charged particles move toward the cathode (negative electrode); negatively charged particles move toward the anode. Used in DNA fingerprinting, protein analysis, and electrophoretic paint deposition.
(a) Coagulation: Aggregation of colloidal particles to form larger particles that settle out of solution. Caused by adding electrolyte (neutralizes charge), heating (increases collisions), or dialysis (removes stabilizing ions). The Hardy-Schulze rule states that coagulating power increases with ion charge. Used in water purification (alum coagulates impurities).
(b) Peptization: Process of converting a freshly precipitated solid into a colloidal solution by adding a small amount of electrolyte (peptizing agent). The electrolyte ions adsorb on precipitate particles, giving them charge and dispersing them. Example: Fe(OH)₃ precipitate + FeCl₃ → Fe(OH)₃ sol.
(c) Dialysis: Purification of colloids by removing dissolved impurities (electrolytes, small molecules) through a semipermeable membrane. Small ions/molecules pass through the membrane; colloidal particles are retained. Electrodialysis uses an electric field to speed up ion removal. Used in artificial kidney (hemodialysis).
(a) Tyndall effect: The path of the light beam becomes visible (as a bright, somewhat bluish streak) passing through the colloid. This is because colloidal particles (1-1000 nm) scatter the light — a phenomenon called the Tyndall effect. The scattered light makes the beam path visible from all directions. Contrast: true solutions don't scatter (no visible path).
(b) Coagulation: The colloid becomes unstable and its particles aggregate to form larger particles that settle down (coagulate). This is because the electrolyte ions neutralize the charge on the colloidal particles, removing the electrostatic repulsion that kept them dispersed. The coagulating power depends on ion charge (Hardy-Schulze rule). This is the principle of water purification — alum (Al³⁺) coagulates impurities.
Emulsions: Colloidal systems where both the dispersed phase and the dispersion medium are liquids (immiscible).
Types:
(1) Oil-in-water (O/W): Oil droplets dispersed in water. Example: milk (fat droplets in water), mayonnaise, vanishing cream.
(2) Water-in-oil (W/O): Water droplets dispersed in oil. Example: butter, cold cream, cod liver oil emulsion.
Stability: Emulsions are stabilized by emulsifying agents (soap, lecithin, proteins, gum arabic) which form a film at the oil-water interface, preventing droplets from coalescing.
Demulsification: Can be broken by heating, adding electrolyte, centrifugation, or demulsifiers.
| Physisorption ΔH | ~−20 kJ/mol | Van der Waals |
| Chemisorption ΔH | ~−200 kJ/mol | Covalent bond |
| Colloid particle size | 1-1000 nm | Between solution & suspension |
| True solution size | <1 nm | No Tyndall |
| Suspension size | >1000 nm | Settles on standing |
| Visible light wavelength | 400-700 nm | Tyndall range |
| Activated charcoal surface area | Up to 3000 m²/g | Extremely high |
| x | Mass of adsorbate |
| m | Mass of adsorbent |
| p | Pressure of gas |
| k, a, b | Constants in isotherms |
| n | Freundlich exponent (>1) |
| CMC | Critical Micelle Concentration |
| O/W | Oil in water emulsion |
| W/O | Water in oil emulsion |
(A) Both true, R explains A. (B) Both true, R does NOT explain A. (C) A true, R false. (D) A false, R true.
All key formulas at one place — perfect for quick revision before competitive exams.