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State Board · Class 11 · Chemistry

Lesson 11: Adsorption and Colloids

7 concepts · 56 practice questions with answers · Free to read

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Adsorption: definition and types

From daily life

The charcoal in a water filter or gas mask traps smells on its surface; that is adsorption.

Simple definition

Adsorption is accumulation of a substance on the surface of a solid or liquid. Adsorbent provides the surface; adsorbate is what sticks. Absorption is uptake throughout the bulk. Desorption is the reverse.

AdsorptionAdsorption: particles stick on the surfaceadsorbentgas/liquid particles (adsorbate)absorptionenter the whole bulkAdsorption = on the surface; absorption = throughout the bulke.g. charcoal adsorbs NH₃; anhydrous CaCl₂ absorbs water

In the figure : Adsorption versus absorption.

Physi vs chemiPhysisorption and chemisorptionFeaturePhysisorptionChemisorptionForcevan der Waalschemical bondEnthalpy20–40 kJ/mol40–200 kJ/molTemperaturehigher at low Tneeds activation, higher TReversibleyesnoLayersmultilayermonolayerSpecificitynot specificspecific

In the figure : Physisorption versus chemisorption.

Rule 1: Physisorption — van der Waals forces; ΔH ≈ 20–40 kJ/mol; reversible; stronger at low T; multilayer; not specific.

  • Easy : Charcoal + NH₃ (low T).
  • Medium : Silica gel drying air.
  • Exam-type : Raising T releases the gas.

Rule 2: Chemisorption — Chemical bonds; ΔH ≈ 40–200 kJ/mol; irreversible; needs activation, higher T; monolayer; specific.

  • Easy : H₂ on Ni (in hydrogenation).
  • Medium : N₂ on Fe (in the Haber process).
  • Exam-type : Physisorption at low T, chemisorption at high T (e.g. H₂ + Ni).

Rule 3: Why is adsorption exothermic? — ΔS < 0 (particles become ordered) and ΔG < 0 ⇒ ΔH = ΔG + TΔS < 0.

  • Easy : Physisorption falls as T rises (Le Chatelier).
  • Medium : More surface area ⇒ more adsorption.
  • Exam-type : Powdered charcoal > a lump.

Reasoning: why is ΔH negative?

  • Step 1: Free gas particles → bound on the surface ⇒ ΔS negative.
  • Step 2: The process occurs ⇒ ΔG = ΔH − TΔS < 0.
  • Step 3: With ΔS negative, ΔH must be even more negative ⇒ exothermic.

CET level (MCQ)

  • CET 1) ΔH of physisorption? 1) 20–40 kJ/mol 2) 40–200 kJ/mol 3) > 400 4) zero — Answer: 1).
  • CET 2) In adsorption? 1) ΔS > 0 2) ΔS < 0 3) ΔH > 0 4) ΔG > 0 — Answer: 2).

Real-life use: Gas masks, water purification, decolourising sugar, silica gel.

Remember

Adsorption = surface; physi 20–40, chemi 40–200; ΔH and ΔS negative.

Common mistake

Swapping adsorption and absorption.

CET trap

Physisorption falls with T; chemisorption first rises, then falls.

Shortcut

Memory clue: "ad = on the surface, ab = into the bulk".

Spot the difference

ItemPhysiChemi
ForcevdWchemical bond
ΔH20–4040–200
Layersmultimono

Practice questions

Easy
  1. 1What is adsorption?
  2. 2Name adsorbent and adsorbate.
  3. 3Two differences between physi and chemisorption.
Medium
  1. 4Why is adsorption exothermic?
  2. 5Why is powdered charcoal more effective?
  3. 6What is desorption?
Challenging
  1. 7Behaviour of H₂ + Ni with T?
  2. 8Use of silica gel?
Show answers (try them yourself first)
  1. 1Accumulation of particles on a surface.
  2. 2Charcoal / gas.
  3. 3Force and ΔH (or reversibility).
  4. 4ΔS < 0 and ΔG < 0.
  5. 5More surface area.
  6. 6Release of adsorbed particles.
  7. 7Physi at low T, chemi at high T.
  8. 8Drying air or gases.

Factors affecting adsorption and the Freundlich isotherm

From daily life

In a crowded bus extra riders must stand; similarly a surface fills up and adsorption saturates.

Simple definition

An isotherm plots amount adsorbed (x/m) against pressure P at constant T. Freundlich: x/m = k·P^(1/n), where x = mass of gas adsorbed and m = mass of adsorbent.

FreundlichFreundlich isotherm: x/m = k·P^(1/n)P →x/mlevels offlog P →log x/mslope = 1/nintercept = log klog(x/m) = log k + (1/n) log Pn > 1; 1/n lies between 0 and 1

In the figure : Freundlich isotherm and its log plot.

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Factors affecting adsorption and the Freundlich isotherm

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Rule 1: Factors — Nature of adsorbate (easily liquefiable gases adsorb more); surface area ↑; pressure ↑ (to saturation); temperature ↑ ⇒ physisorption ↓.

  • Easy : NH₃, SO₂ adsorb more; H₂, N₂ less.
  • Medium : Activated charcoal is best.
  • Exam-type : x/m falls as T rises.

Rule 2: Freundlich equation — log(x/m) = log k + (1/n) log P; slope = 1/n, intercept = log k. Low P: x/m ∝ P; high P: x/m ≈ constant.

  • Easy : k = 2, 1/n = 0.5, P = 4 ⇒ x/m = 2 × 2 = 4.
  • Medium : log k = 0.3 ⇒ k ≈ 2.
  • Exam-type : P = 9 ⇒ x/m = 2 × 3 = 6.

Rule 3: Limitations — Freundlich is empirical and fails at very high pressure. Langmuir assumes a monolayer and gives saturation.

  • Easy : 1/n = 0 ⇒ x/m constant (saturated).
  • Medium : 1/n = 1 ⇒ x/m ∝ P.
  • Exam-type : n > 1 so 1/n < 1.

Calculation: k and 1/n from the graph

  • Step 1: log(x/m) against log P is a straight line.
  • Step 2: slope = 1/n = 0.5; intercept = 0.3.
  • Step 3: k = 10^0.3 ≈ 2; P = 4 ⇒ x/m = 2 × 4^0.5 = 4.

CET level (MCQ)

  • CET 1) Slope of log(x/m) against log P? 1) n 2) 1/n 3) k 4) log k — Answer: 2).
  • CET 2) k = 2, 1/n = 0.5, P = 9: x/m? 1) 3 2) 4 3) 6 4) 18 — Answer: 3).

Real-life use: Industrial gas purification, choosing charcoal filters.

Remember

slope 1/n; intercept log k; 0 < 1/n < 1; T ↑ physi ↓.

Common mistake

Writing the slope as n; it is 1/n.

CET trap

Use log₁₀ and note 1/n = 0.5 is a square root.

Shortcut

Memory clue: "slope = one over n".

Spot the difference

Px/m
low∝ P
medium∝ P^(1/n)
highconstant

Practice questions

Easy
  1. 1What is an isotherm?
  2. 2Write the Freundlich equation.
  3. 3How do you get k from the graph?
Medium
  1. 4k = 2, 1/n = 0.5, P = 4: x/m?
  2. 5Why does physisorption fall as T rises?
  3. 6Why is NH₃ adsorbed more?
Challenging
  1. 7Meaning of 1/n = 0?
  2. 8Langmuir versus Freundlich.
Show answers (try them yourself first)
  1. 1x/m against P at constant T.
  2. 2x/m = k P^(1/n).
  3. 3Intercept = log k.
  4. 44.
  5. 5The process is exothermic.
  6. 6It is easily liquefied.
  7. 7x/m is constant.
  8. 8Langmuir assumes a monolayer.

Catalysis: homogeneous, heterogeneous and enzymes

From daily life

A spoonful of curd turns milk into curd faster; it acts like a catalyst.

Simple definition

A catalyst speeds up a reaction, is unchanged at the end, and lowers activation energy; ΔH and K are unchanged. Enzymes are biological catalysts (proteins).

CatalysisCatalysisHomogeneous2SO₂ + O₂ →(NO) 2SO₃all in one phaseHeterogeneousN₂ + 3H₂ →(Fe) 2NH₃catalyst in another phaseEnzyme: lock-and-key / induced fitenzymeSESproduct + enzymeA catalyst lowers activation energy; ΔH and K are unchangede.g. starch + amylase → maltose; 310 K, pH ≈ 7

In the figure : Homogeneous, heterogeneous and enzyme catalysis.

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Catalysis: homogeneous, heterogeneous and enzymes

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Rule 1: Types — Homogeneous: same phase; heterogeneous: different phases (adsorption on the surface).

  • Easy : 2SO₂ + O₂ →(NO) 2SO₃: homogeneous.
  • Medium : N₂ + 3H₂ →(Fe) 2NH₃: heterogeneous.
  • Exam-type : Autocatalysis: KMnO₄ + oxalic acid (Mn²⁺).

Rule 2: Steps of heterogeneous catalysis — Diffusion → adsorption → surface reaction → desorption → diffusion of products. Promoters enhance; poisons reduce activity.

  • Easy : Mo promotes Fe.
  • Medium : As and S compounds poison Pt.
  • Exam-type : More catalyst surface ⇒ faster.

Rule 3: Enzymes — Highly specific (lock-and-key / induced fit); optimum T ≈ 310 K and pH; E + S ⇌ ES → E + P.

  • Easy : Starch + amylase → maltose.
  • Medium : Urea + urease → NH₃ + CO₂.
  • Exam-type : High T denatures the enzyme.

Why does a catalyst not change K?

  • Step 1: It lowers Eₐ of both forward and reverse reactions.
  • Step 2: Both rates rise by the same factor.
  • Step 3: K = k₁/k₂ stays the same; equilibrium is just reached sooner.

CET level (MCQ)

  • CET 1) Catalysis in the Haber process is? 1) homogeneous 2) heterogeneous 3) enzymatic 4) auto — Answer: 2).
  • CET 2) A catalyst does not change? 1) Eₐ 2) rate 3) ΔH 4) mechanism — Answer: 3).

Real-life use: Catalytic converters (Pt/Pd), digestive enzymes, industrial Ni and Fe.

Remember

Eₐ ↓; ΔH, K same; heterogeneous = adsorption; enzyme at 310 K.

Common mistake

Writing that a catalyst raises K.

CET trap

A promoter is not itself the catalyst; it helps the catalyst.

Shortcut

Memory clue: "catalyst = speed only".

Spot the difference

ItemHomogeneousHeterogeneous
Phasesamedifferent
ExampleNOFe

Practice questions

Easy
  1. 1What is a catalyst?
  2. 2An example of homogeneous catalysis.
  3. 3What is a promoter?
Medium
  1. 4What is a catalytic poison?
  2. 5Why are enzymes specific?
  3. 6An example of autocatalysis.
Challenging
  1. 7Why doesn't a catalyst change K?
  2. 8Optimum T for enzymes?
Show answers (try them yourself first)
  1. 1A substance that raises rate and is unchanged.
  2. 22SO₂ + O₂ with NO.
  3. 3One that boosts the catalyst.
  4. 4One that reduces activity.
  5. 5The active site has a specific shape.
  6. 6KMnO₄ + oxalic acid.
  7. 7Both directions rise equally.
  8. 8≈ 310 K.

Colloids: classification and properties

From daily life

Milk, fog, smoke and jelly are colloids; neither a true solution nor a suspension.

Simple definition

Colloid: particle size 1–1000 nm (the textbook text says 2–500 nm; solutions 0.1–2 nm); heterogeneous; dispersed phase in a dispersion medium. Lyophilic (solvent-loving) are stable; lyophobic are unstable.

Colloid typesColloids: types (dispersed phase / medium)Typedispersed / mediumexampleSolsolid / liquidpaint, starch solGelliquid / solidjelly, cheeseEmulsionliquid / liquidmilk, butterFoamgas / liquidshaving creamAerosolliquid/solid / gasfog, smokeParticle size: 1 nm – 1000 nm (10⁻⁹ to 10⁻⁶ m)solution < 1 nm; suspension > 1000 nm

In the figure : Types of colloids.

TyndallTyndall effect and Brownian motionTrue solution: beam invisibleColloid: beam visibleReason: colloidal particles scatter light (size ≈ λ)Brownian motion: random zigzagMedium molecules hit the particle ⇒ motionkeeps the sol stable (no settling)e.g. smoke particles

In the figure : Tyndall effect and Brownian motion.

Rule 1: Classification — By phase: sol, gel, emulsion, foam, aerosol. By particles: multimolecular (gold sol), macromolecular (starch), associated (soap).

  • Easy : Milk: liquid-in-liquid emulsion.
  • Medium : Fog: liquid-in-gas aerosol.
  • Exam-type : Jelly: liquid-in-solid gel.

Rule 2: Optical and kinetic properties — Tyndall effect: particles scatter light ⇒ visible beam. Brownian motion: medium molecules bombard particles ⇒ zigzag; keeps the sol stable.

  • Easy : Sunbeams visible through a misty forest.
  • Medium : True solution: no Tyndall effect.
  • Exam-type : Dust shows Brownian motion.

Rule 3: Electrical properties — Colloidal particles carry a like charge ⇒ mutual repulsion ⇒ stability. Electrophoresis: particle movement in an electric field.

  • Easy : As₂S₃ is negative; Fe(OH)₃ is positive.
  • Medium : Fe(OH)₃ sol moves to the cathode.
  • Exam-type : Blood purification (dialysis).

Classification by particle size

  • Step 1: < 1 nm ⇒ true solution.
  • Step 2: 1–1000 nm ⇒ colloid.
  • Step 3: > 1000 nm ⇒ suspension.

CET level (MCQ)

  • CET 1) Colloidal particle size? 1) < 1 nm 2) 1–1000 nm 3) > 1 μm 4) 10 μm — Answer: 2).
  • CET 2) Milk is a? 1) sol 2) emulsion 3) gel 4) foam — Answer: 2).

Real-life use: Paints, inks, medicines, fog, dairy processing.

Remember

1–1000 nm; Tyndall; Brownian; like charge ⇒ stable.

Common mistake

Calling a colloid a true solution; it is heterogeneous.

CET trap

Milk = emulsion; jelly = gel (liquid dispersed in solid).

Shortcut

Memory clue: "one to one-thousand nm".

Spot the difference

TypeSizeTyndall
Solution< 1 nmno
Colloid1–1000 nmyes
Suspension> 1000 nmyes

Practice questions

Easy
  1. 1What is a colloid?
  2. 2State the Tyndall effect.
  3. 3Cause of Brownian motion?
Medium
  1. 4State the type of milk.
  2. 5Lyophilic versus lyophobic.
  3. 6What is electrophoresis?
Challenging
  1. 7An example of an aerosol.
  2. 8Why is a colloid stable?
Show answers (try them yourself first)
  1. 1A heterogeneous system with 1–1000 nm particles.
  2. 2Particles scatter light.
  3. 3Medium molecules collide.
  4. 4Emulsion.
  5. 5Solvent-loving stable; solvent-hating unstable.
  6. 6Particle movement in an electric field.
  7. 7Fog or smoke.
  8. 8Like charge; Brownian motion.

Preparation and purification of colloids

From daily life

Buttermilk and fridge fog show how colloids form and break.

Simple definition

Preparation: (1) condensation — joining small particles, (2) dispersion — breaking large ones. Purification: removing ions — dialysis, ultrafiltration, ultracentrifugation.

Rule 1: Condensation methods — Double decomposition: As₂O₃ + 3H₂S → As₂S₃ sol + 3H₂O; oxidation: SO₂ + 2H₂S → 3S sol + 2H₂O; hydrolysis: FeCl₃ + 3H₂O → Fe(OH)₃ sol + 3HCl.

  • Easy : FeCl₃ in hot water gives a reddish sol.
  • Medium : As₂S₃ is a yellow sol.
  • Exam-type : Sulphur sol is milky.

Rule 2: Dispersion methods — Bredig's arc: electric arc between metal electrodes under water ⇒ metal sol. Peptization: a little electrolyte turns a fresh precipitate into a sol.

  • Easy : Fe(OH)₃ precipitate + a little FeCl₃ ⇒ sol.
  • Medium : Au, Ag, Pt sols by arc.
  • Exam-type : Colloid mill: mechanical dispersion.

Rule 3: Purification — Dialysis: semipermeable membrane lets small ions out; ultrafiltration: special filters; ultracentrifugation: very fast spinning.

  • Easy : Kidney dialysis.
  • Medium : Removing HCl from a sol.
  • Exam-type : Protein purification by ultracentrifugation.

Reasoning: how does peptization work?

  • Step 1: A fresh precipitate is a clump of particles.
  • Step 2: A few ions adsorb on the particles and give them charge.
  • Step 3: Like charges repel ⇒ particles separate into a sol.

CET level (MCQ)

  • CET 1) Bredig's arc is for? 1) metal sols 2) emulsions 3) gels 4) foams — Answer: 1).
  • CET 2) Method for the Fe(OH)₃ sol? 1) hydrolysis 2) oxidation 3) arc 4) centrifugation — Answer: 1).

Real-life use: Paints, inks, medicines, dialysis machines.

Remember

Condensation and dispersion; Bredig = metals; peptization; dialysis.

Common mistake

Not recognising that peptization is the reverse of coagulation.

CET trap

Dialysis removes ions, not colloidal particles.

Shortcut

Memory clue: "condense = join, disperse = break".

Spot the difference

MethodUse
Bredigmetal sol
Peptizationprecipitate → sol
Dialysispurification

Practice questions

Easy
  1. 1What are condensation methods?
  2. 2What is Bredig's arc?
  3. 3What is peptization?
Medium
  1. 4How is the Fe(OH)₃ sol made?
  2. 5Why is dialysis done?
  3. 6What is ultracentrifugation?
Challenging
  1. 7How is As₂S₃ sol prepared?
  2. 8How is a sulphur sol prepared?
Show answers (try them yourself first)
  1. 1Making colloids by joining particles.
  2. 2Metal sols by electric arc.
  3. 3Converting a precipitate to a sol.
  4. 4Hydrolysis of FeCl₃ in hot water.
  5. 5To remove impurity ions.
  6. 6Separating by very fast spinning.
  7. 7As₂O₃ + H₂S.
  8. 8Oxidation of H₂S by SO₂.

Coagulation, Hardy–Schulze rule and gold number

From daily life

Squeezing lemon into milk curdles it; that is coagulation.

Simple definition

Coagulation: neutralising the charge on colloidal particles so they clump. Hardy–Schulze: coagulating power rises with the charge of the counter-ion. Gold number: minimum mg of protective colloid that stops coagulation of 10 mL gold sol.

CoagulationCoagulation and micelleHardy–Schulze rule: coagulating power ∝ counter-ion chargeFor negative As₂S₃ sol: Al³⁺ > Ba²⁺ > Na⁺For positive Fe(OH)₃ sol: [Fe(CN)₆]⁴⁻ > PO₄³⁻ > SO₄²⁻ > Cl⁻oily coresoap micelleMicelles form above the CMCFor soaps CMC ≈ 10⁻⁴ – 10⁻³ mol/Lhydrophilic head out; hydrophobic tail incleaning: grease trapped in the core

In the figure : Coagulation rule and micelle.

Rule 1: Hardy–Schulze rule — For negative sols: Al³⁺ > Ba²⁺ > Na⁺; for positive sols: [Fe(CN)₆]⁴⁻ > PO₄³⁻ > SO₄²⁻ > Cl⁻.

  • Easy : AlCl₃ is the most effective on As₂S₃.
  • Medium : K₄[Fe(CN)₆] for Fe(OH)₃.
  • Exam-type : Delta formation at river mouths.

Rule 2: Gold number — The smaller the gold number, the better the protective colloid.

  • Easy : Gelatin 0.005–0.01; starch 25.
  • Medium : Gelatin is a better protector than starch.
  • Exam-type : Gelatin in ice cream.

Rule 3: Applications of coagulation — Alum (Al³⁺) clears muddy water; Fe³⁺ stops bleeding; Cottrell precipitator removes smoke particles.

  • Easy : Alum + muddy water.
  • Medium : Applying alum on a cut.
  • Exam-type : Removing ash from factory smoke.

Why is Al³⁺ more effective than Na⁺?

  • Step 1: Positive ions are needed to neutralise negative particles.
  • Step 2: Al³⁺ carries +3, so fewer ions neutralise the charge.
  • Step 3: So a lower concentration suffices (lower flocculation value).

CET level (MCQ)

  • CET 1) Most effective on As₂S₃ sol? 1) NaCl 2) BaCl₂ 3) AlCl₃ 4) KCl — Answer: 3).
  • CET 2) Best protective colloid has gold number? 1) 25 2) 0.01 3) 5 4) 10 — Answer: 2).

Real-life use: Water clarification, alum on cuts, smoke cleaning, ice cream.

Remember

Negative sol ⇒ Al³⁺; positive sol ⇒ [Fe(CN)₆]⁴⁻; small gold number ⇒ better.

Common mistake

Saying a large gold number means more protection; it is the opposite.

CET trap

The counter-ion has charge opposite to the sol.

Shortcut

Memory clue: "bigger charge, bigger coagulation".

Spot the difference

SolBest ion
As₂S₃ (−)Al³⁺
Fe(OH)₃ (+)[Fe(CN)₆]⁴⁻

Practice questions

Easy
  1. 1What is coagulation?
  2. 2State the Hardy–Schulze rule.
  3. 3What is the gold number?
Medium
  1. 4Why does alum clear water?
  2. 5How does a delta form?
  3. 6Compare gold numbers of gelatin and starch.
Challenging
  1. 7Best ion for Fe(OH)₃?
  2. 8What does a Cottrell precipitator do?
Show answers (try them yourself first)
  1. 1Particles lose charge and settle.
  2. 2Higher counter-ion charge, stronger coagulation.
  3. 3Minimum mg of protective colloid for 10 mL gold sol.
  4. 4Al³⁺ neutralises the mud particles.
  5. 5Sea ions coagulate river silt.
  6. 6Gelatin is smaller ⇒ better.
  7. 7[Fe(CN)₆]⁴⁻.
  8. 8It precipitates smoke particles.

Emulsions, micelles and applications of colloids

From daily life

Soap cleans a greasy plate because its molecules trap oil inside micelles.

Simple definition

An emulsion is one liquid dispersed in another (oil/water). An emulsifier stabilises it. A micelle is an associated colloid of soap or detergent that forms above the CMC (critical micelle concentration).

Rule 1: Types of emulsions — O/W: oil in water (milk); W/O: water in oil (butter, cold cream). Emulsifiers: soap, casein, gelatin.

  • Easy : Milk is O/W; butter is W/O.
  • Medium : Mayonnaise: egg lecithin.
  • Exam-type : Dilution test: mixes with water ⇒ O/W.

Rule 2: Soap and micelles — Soap RCOO⁻Na⁺: hydrophobic tail + hydrophilic head; in a micelle the oil sits inside and the heads face out. Micelles form only above a certain temperature (the Kraft temperature).

  • Easy : For soaps CMC ≈ 10⁻⁴–10⁻³ mol/L.
  • Medium : Micelle size is colloidal.
  • Exam-type : Soap lathers poorly in hard water (Ca²⁺ precipitate).

Rule 3: Applications — Medicines (colloidal silver), rubber latex, tanning leather, artificial rain, smoke removal, food processing.

  • Easy : Tanning: coagulation of the colloid.
  • Medium : Cloud seeding: AgI particles in clouds.
  • Exam-type : Coagulating latex gives rubber.

Why do micelles form only above the CMC?

  • Step 1: At low concentration soap ions sit singly at the surface.
  • Step 2: Once the surface is full, tails huddle inside to avoid water.
  • Step 3: Above the CMC micelles form and cleaning power rises.

CET level (MCQ)

  • CET 1) Butter is which emulsion? 1) O/W 2) W/O 3) sol 4) gel — Answer: 2).
  • CET 2) In a micelle the oil is? 1) outside 2) inside 3) in water 4) in air — Answer: 2).

Real-life use: Soap, detergents, butter, medicines, leather, cloud seeding.

Remember

Milk O/W; butter W/O; micelles above CMC; oil in, heads out.

Common mistake

Writing that hydrophilic heads face inward; they face outward.

CET trap

Soap precipitates with Ca²⁺ in hard water; detergents do not.

Shortcut

Memory clue: "tail in, head out".

Spot the difference

ItemO/WW/O
Examplemilkbutter
Mixes with wateryesno

Practice questions

Easy
  1. 1What is an emulsion?
  2. 2What is an emulsifier?
  3. 3What is a micelle?
Medium
  1. 4What is the CMC?
  2. 5How does soap remove grease?
  3. 6How is artificial rain made?
Challenging
  1. 7Why does soap work poorly in hard water?
  2. 8Emulsion types of milk and butter.
Show answers (try them yourself first)
  1. 1One liquid dispersed in another.
  2. 2A substance stabilising an emulsion.
  3. 3An associated colloid of soap molecules.
  4. 4Critical micelle concentration.
  5. 5The grease is trapped inside the micelle.
  6. 6AgI particles are sprayed into clouds.
  7. 7Ca²⁺ precipitates the soap.
  8. 8O/W and W/O.

Quick revision of the whole lesson

ConceptKey formula / fact
Adsorptionsurface; physi 20–40, chemi 40–200 kJ/mol
Freundlichx/m = k P^(1/n)
CatalystEₐ ↓; ΔH, K same
Colloid1–1000 nm
PreparationBredig, peptization
Hardy–SchulzeAl³⁺ > Ba²⁺ > Na⁺
Gold numbersmall ⇒ better
Micelleabove CMC; oil in
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🚀 Quick revision of the whole lesson

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🎯 Most important points for the exam

  • Adsorption and types.
  • Freundlich isotherm.
  • Catalysis and enzymes.
  • Colloid classification and properties.
  • Preparation and purification.
  • Coagulation and gold number.
  • Emulsions, micelles, uses.
Study mantra

understand the idea → remember the formula → solve the example → solve problems yourself.