MCQs on Colloidal Dispersions GPAT / NIPER / AIIMS / HSSB / SSB / RRB / DSSSB / Pharmacist Recruitment Exams.

1. The colloidal dispersion particle size range:

A. Less than 1 nm
B. 1–100 µm
C. 1–1000 nm
D. Greater than 1000 µm

Answer: B

Explanation:

Colloidal dispersions contain particles with sizes ranging from 1 nanometer (nm) to 1000 nm (1 µm). These particles are intermediate in size between true solutions and suspensions.

• True solutions: particle size less than 1 nm

• Colloidal dispersions: particle size 1–1000 nm

• Suspensions: particle size more than 1000 nm

Because colloidal particles are small enough to remain dispersed yet large enough to scatter light, they exhibit properties such as the Tyndall effect and Brownian movement.

GPAT Tip:

Remember the simple sequence:

True solution < Colloid < Suspension

<1 nm∣1–1000 nm∣>1000 nm

This classification is frequently asked in exams.

2. Select a suitable example of a lyophilic colloid.

A. Gelatin solution
B. Sulfur sol
C. Gold sol
D. Arsenic sulfide sol

Answer: C

Explanation:

Lyophilic colloids are “solvent-loving” colloids in which the dispersed phase has a strong affinity for the dispersion medium. These colloids are usually stable, reversible, and easy to prepare.

Gelatin solution is a classic example of a lyophilic colloid because gelatin readily interacts with water and forms a stable colloidal system.

Other Options:

• Gold sol: Lyophobic colloid

• Sulfur sol: Lyophobic colloid

• Arsenic sulfide sol: Lyophobic colloid

Lyophobic colloids have little affinity for the solvent and are comparatively unstable.

GPAT Tip:

Remember:

• Lyophilic = solvent-loving = stable

• Examples: Gelatin, starch, gum, proteins

• Lyophobic = solvent-hating

• Examples: Gold sol, sulfur sol, As₂S₃ sol

A common trick is asking to identify lyophilic vs lyophobic colloids from examples.

3. A characteristic of lyophobic colloids is

A. Reversible nature
B. High viscosity
C. Low stability
D. High affinity for dispersion medium

Answer: C

Explanation:

Lyophobic colloids are “solvent-hating” colloids in which the dispersed phase has very little affinity for the dispersion medium. Because of this weak interaction, these colloids are generally less stable and can be easily precipitated by small amounts of electrolytes.

Why Other Options Are Incorrect:

• A. High affinity for dispersion medium: Characteristic of lyophilic colloids

• B. Reversible nature: Lyophobic colloids are usually irreversible

• D. High viscosity: More commonly associated with lyophilic colloids

Features of Lyophobic Colloids:

• Low affinity for solvent

• Irreversible

• Low stability

• Easily coagulated

• Require special preparation methods

GPAT Tip:

Quick comparison for exams:

• Property Lyophilic Lyophobic

• Affinity for solvent High Low

• Stability High Low

• Reversibility Reversible Irreversible

• Viscosity High Nearly same as solvent

Examples of lyophobic colloids: Gold sol, sulfur sol, arsenic sulfide sol.

4. The concentration above which micelles are formed is known as the:

A. Triple point
B. Cloud point
C. Krafft's point
D. CMC

Answer: D

Explanation:

Micelles are formed when surfactant molecules aggregate in solution after reaching a specific concentration called the critical micelle concentration (CMC).

Below the CMC, surfactants exist mainly as individual molecules. Above the CMC, they associate to form micelles, where

• Hydrophobic tails face inward

• Hydrophilic heads face outward toward water

Micelle formation is important in the following:

• Solubilization

• Detergency

• Emulsification

• Drug delivery systems

Why Other Options Are Incorrect:

• A. Krafft point → Minimum temperature required for micelle formation in ionic surfactants

• B. Cloud point → Temperature at which nonionic surfactant solutions become cloudy

• D. Triple point → Temperature and pressure where solid, liquid, and gas coexist

GPAT Tip:

Remember:

• CMC: Concentration

• Krafft point: Temperature

A common GPAT conceptual question is the difference between the CMC and Krafft point.

Micelle formation can be represented as:

Surfactant molecules = above CMC​ Micelles

5. The phenomenon of scattering light by colloidal particles is:

A. Electrophoresis
B. Diffusion
C. Tyndall effect
D. Brownian movement

Answer: C

Explanation:

The Tyndall effect is the scattering of light by colloidal particles when a beam of light passes through a colloidal system. Because colloidal particles are large enough to scatter light, the path of the light beam becomes visible.

This property helps distinguish the following:

• Colloidal dispersions: show Tyndall effect

• True solutions: do not show the Tyndall effect

Why Other Options Are Incorrect:

• A. Brownian movement: Random zig-zag movement of colloidal particles

• C. Diffusion: Movement of particles from higher to lower concentration

• D. Electrophoresis: Movement of charged colloidal particles under an electric field

GPAT Tip:

Associate these terms quickly:

• Property Meaning

• Tyndall effect: Scattering of light

• Brownian movement: Random particle motion

• Electrophoresis: Movement in an electric field

A frequent GPAT question is:
“Which property confirms the colloidal nature of a system?”
Tyndall effect is the most common answer

6. The zig-zag movement of particles in a colloid system is known as:

A. Dialysis
B. Cataphoresis
C. Brownian motion
D. Sedimentation

Answer: C

Explanation:

Brownian motion refers to the continuous random zig-zag movement of colloidal particles in a dispersion medium. This movement occurs because the particles are constantly bombarded unevenly by molecules of the surrounding medium.

Brownian motion helps in:

• Preventing sedimentation

• Maintaining colloidal stability

Why Other Options Are Incorrect:

• A. Dialysis → Separation of small dissolved substances through a semipermeable membrane

• B. Cataphoresis → Movement of charged colloidal particles under an electric field

• D. Sedimentation → Settling of particles under gravity

GPAT Tip:

Frequently asked colloidal terms:

• Term Meaning

• Brownian motion: Zig-zag particle movement

• Tyndall effect: Scattering of light

• Electrophoresis/Cataphoresis: Movement in electric field

• Dialysis: Purification of colloids

Brownian movement concept:

Unequal molecular bombardment TO random zig-zag movement

7. Which property contributes to the colloidal dispersion's stability?

A. Electrostatic charge
B. Large particle size
C. High density
D. Low viscosity

Answer: C

Explanation:

Colloidal particles usually carry an electrostatic charge on their surface. Since similarly charged particles repel each other, aggregation is prevented, thereby maintaining the stability of the colloidal dispersion.

Why Other Options Are Incorrect:

• B. Large particle size → Larger particles tend to settle easily and decrease stability

• C. High density → Promotes sedimentation rather than stability

• D. Low viscosity → Does not significantly stabilize colloidal systems

GPAT Tip:

In pharmaceutical colloids, stability is mainly due to

• Electrostatic repulsion

• Brownian motion

• Hydration/solvation layer (in lyophilic colloids)

Important exam concept:

Like charges→repulsion→colloidal stability

8. The gold number is associated with:

A. Colloidal viscosity
B. Colloidal protective action
C. Colloidal particle size
D. Colloidal Osmotic Pressure

Answer: B

Explanation:

The gold number is a measure of the protective power of a lyophilic colloid in preventing the coagulation of a gold sol by an electrolyte.

It is defined as:

The minimum amount (in mg) of a protective colloid required to prevent the coagulation of 10 mL of standard gold sol after the addition of 1 mL of 10% sodium chloride solution.

• Lower gold number: Greater protective action

• Higher gold number: Lower protective action

Why Other Options Are Incorrect:

• A. Colloidal viscosity: Related to flow properties, not gold number

• C. Colloidal particle size: Measured by ultramicroscopy or light scattering methods

• D. Colloidal osmotic pressure → Related to concentration and molecular weight

GPAT Tip:

Remember:

“Gold number = Protective power."

Examples of protective colloids:

• Gelatin

• Starch

• Gum acacia

A lower gold number indicates better protection:

Lower gold number: Higher protective action

9. The lower the gold number indicates

A. Lower the conductivity
B. The greater the viscosity
C. The higher the protective power
D. Lower the protective power

Answer: C

Explanation:

The gold number measures the protective ability of a lyophilic colloid toward a gold sol.

• A lower gold number means only a small amount of protective colloid is needed to prevent coagulation.

• Therefore, the colloid has greater protective power.

Why Other Options Are Incorrect:

• A. Lower the conductivity: Gold number is unrelated to conductivity

• B. The greater the viscosity: Not directly measured by gold number

• D. Lower the protective power: Opposite of the correct concept

GPAT Tip:

Easy memory trick:

“Less quantity needed = More efficient protection."

Hence,

Gold number ∝ 1/Protective power

Examples:

• Gelatin: Low gold number: Excellent protective colloid

• Starch: Higher gold number compared to gelatin

10. Which instrument is used for the particle size determination of colloids by light scattering?

A. Nephelometer
B. Colorimeter
C. Pycnometer
D. Polarimeter

Answer: A

Explanation:

A nephelometer is an instrument used to determine the particle size and concentration of colloidal dispersions by measuring the light scattered by suspended particles.

The intensity of scattered light depends on:

• Number of particles

• Particle size

• Wavelength of light

Nephelometry is commonly applied in:

• Colloidal analysis

• Immunoassays

• Pharmaceutical suspensions

Why Other Options Are Incorrect:

• B. Colorimeter: Measures absorbance or color intensity of solutions

• C. Pycnometer: Used for the determination of specific gravity/density

• D. Polarimeter: Measures the optical rotation of optically active substances

GPAT Tip:

Remember the relation:

• Tyndall effect → Scattering of light

• Nephelometer → Measures scattered light

Light scattering principle:

Intensity of scattered light ∝ particle concentration and size

11. Electrophoresis is the study of:

A. Charged particles' movement in an electric field
B. Electrical resistance of preparation
C. Osmotic pressure of preparation
D. Optical properties of preparation

Answer: B

Explanation:

Electrophoresis is the phenomenon in which charged colloidal particles move toward the oppositely charged electrode when an electric field is applied.

• Positively charged particles move toward the cathode.

• Negatively charged particles move toward the anode.

Electrophoresis is used to:

• Determine the charge on colloidal particles

• Study stability of colloids

• Separate biomolecules such as proteins and nucleic acids

Why Other Options Are Incorrect:

• B. Electrical resistance of preparation: Related to conductivity measurements

• C. Osmotic pressure of preparation: Related to colligative properties

• D. Optical properties of preparation: Includes Tyndall effect and light scattering

GPAT Tip:

Do not confuse:

• Term Meaning

• Electrophoresis: Movement of charged particles in an electric field

• Electroosmosis: Movement of the dispersion medium

• Cataphoresis: Another term for electrophoresis

Electrophoresis concept:

Charged colloidal particles + Electric field: Particle migration

12. Select a colloidal system that consists of a solid dispersed in a liquid.

A. Aerosol
B. Sol
C. Emulsion
D. Foam

Answer: B. Sol

Explanation:

A sol is a colloidal system in which a solid is dispersed in a liquid.

Examples:

• Paints

• Starch sol

• Gold sol

Why Other Options Are Incorrect:

• A. Aerosol → Solid or liquid dispersed in gas

• C. Emulsion → Liquid dispersed in another liquid

• D. Foam → Gas dispersed in liquid or solid

GPAT Tip:

Important colloidal classifications:

• Dispersed Phase Dispersion Medium System

• Solid Liquid Sol

• Liquid Liquid Emulsion

• Gas Liquid Foam

• Solid/Liquid Gas Aerosol

Classification of sol:

Solid + Liquid: Sol

13. Milk is an example of

A. Solid sol
B. Gel
C. Emulsion
D. Natural emulsion

Answer: D

Explanation:

Milk is a natural emulsion in which tiny fat globules are dispersed in water. It is specifically an oil-in-water (O/W) emulsion because fat droplets are dispersed throughout the aqueous phase.

Milk contains natural emulsifying agents such as proteins and phospholipids that help stabilize the emulsion.

Why Other Options Are Incorrect:

• A. Solid sol → Solid dispersed in solid

• B. Gel → Liquid dispersed in a solid, forming a semi-solid system

• C. Emulsion → General term, but milk is more specifically classified as a natural emulsion

GPAT Tip:

Remember common examples:

• System Example

• Sol Paint

• Gel Jelly

• Emulsion Cream

• Natural emulsion Milk

Milk classification:

Oil droplets dispersed in water: O/W emulsion

14. The process to convert a precipitate into a colloidal sol is called:

A. Electrolysis
B. Dialysis
C. Coagulation
D. Peptization

Answer: C

Explanation:

Peptization is the process of converting a freshly formed precipitate into a colloidal sol by adding a small amount of electrolyte called a peptizing agent.

The peptizing agent adsorbs on the surface of precipitated particles, giving them charge and causing them to disperse into colloidal size.

Example:
Fe(OH)₃ precipitate + FeCl₃ ​= Ferric hydroxide sol

Why Other Options Are Incorrect:

• A. Electrolysis → Chemical decomposition by electric current

• B. Dialysis → Purification of colloids through a semipermeable membrane

• C. Coagulation → Aggregation and precipitation of colloidal particles

GPAT Tip:

Do not confuse:

• Process Meaning

• Peptization Precipitate = Colloidal sol

• Coagulation Colloidal sol = Precipitate

• Dialysis Purification of colloids

Peptization process:

Precipitate + Peptizing agent: Colloidal sol

15. The charge on colloidal particles is due to:

A. Ion Adsorption on Colloidal Particles
B. Alkalinization and acidification
C. Neutralization
D. Friction force

Answer: A

Explanation:

The charge on colloidal particles mainly arises due to the adsorption of ions from the surrounding medium onto the surface of colloidal particles.

For example:

• If colloidal particles adsorb positive ions, they become positively charged.

• If they absorb negative ions, they become negatively charged.

This surface charge is responsible for:

• Stability of colloids

• Electrophoresis

• Formation of the electrical double layer

Why Other Options Are Incorrect:

• B. Alkalinization and acidification → May influence charge, but are not the primary cause

• C. Neutralization → Reduces or removes charge

• D. Friction force → Not responsible for colloidal charge formation

GPAT Tip:

Important concept:

Charge on colloids = Repulsion = Stability

The origin of charge is commonly asked in exams.

Surface charge formation:

Ion adsorption on particle surface = Surface charge

16. Which one of the electrolytes has the highest coagulating power for negatively charged sols according to the Hardy-Schulze rule?

A. NaCl
B. KCl
C. AlCl₃
D. BaCl₂

Answer: C

Explanation:

According to the Hardy–Schulze rule, the coagulating power of an electrolyte depends on the valency of the ion carrying the charge opposite to that of the colloidal particles.

For a negatively charged sol, the coagulating ion is the cation.

Cation valencies in the options:

• NaCl = Na⁺ (valency = 1)

• KCl = K⁺ (valency = 1)

• BaCl₂ = Ba²⁺ (valency = 2)

• AlCl₃ = Al³⁺ (valency = 3)

Higher valency means greater coagulating power. Therefore, Al³⁺ has the highest coagulating power.

GPAT Tip:

Remember the order for negatively charged sols:

Al3+ >Ba2+ >Na+

Higher valency of oppositely charged ions = Greater coagulation power.

Hardy–Schulze rule:

Coagulating power ∝ Valency of oppositely charged ions

17. The visibility of colloidal particles under an ultramicroscope due to:

A. Light Polarization
B. Light Reflection
C. Light Scattering
D. Light Refraction

Answer: C

Correct Answer: C. Light Scattering

Explanation:

Colloidal particles are visible under an ultramicroscope because they scatter light passing through the colloidal system. This phenomenon is related to the Tyndall effect.

Although the particles themselves may not be directly seen, the scattered light makes them appear as bright spots against a dark background.

Why Other Options Are Incorrect:

• A. Light Polarization → Related to wave orientation, not particle visibility

• B. Light Reflection → Not the main principle involved

• D. Light Refraction → Bending of light, not responsible for ultramicroscopic visibility

GPAT Tip:

Link these concepts together:

• Concept Related Principle

• Tyndall effect: Light scattering

• Ultramicroscope: Observation by scattered light

• Nephelometer: Measurement of scattered light

Ultramicroscope principle: Incident light = Scattering by colloidal particles = Visibility

18. Which kinetic property is responsible for the diffusion of colloidal particles?

A. Electrophoresis
B. Active diffusion
C. Tyndal effect
D. Brownian motion

Answer: B

Explanation:

Brownian motion is the continuous random zig-zag movement of colloidal particles caused by unequal bombardment from molecules of the dispersion medium. This kinetic activity is responsible for the diffusion of colloidal particles throughout the system.

Brownian motion helps:

• Maintain uniform distribution

• Prevent sedimentation

• Enhance diffusion in colloidal systems

Why Other Options Are Incorrect:

• A. Electrophoresis → Movement of charged particles under electric field

• B. Active diffusion → Not a standard colloidal property term

• C. Tyndall effect → Scattering of light by colloidal particles

GPAT Tip:

Important kinetic properties of colloids:

• Property Function

• Brownian motion: Diffusion and stability

• Diffusion: Movement from high to low concentration

• Sedimentation: Settling under gravity

Brownian movement and diffusion:

Brownian motion = Enhanced diffusion of colloidal particles

19. Select an irreversible colloid

A. Gelatin sol
B. Starch sol
C. Acacia sol
D. Ferric hydroxide sol

Answer: D

Explanation:

Ferric hydroxide sol is a lyophobic colloid, and lyophobic colloids are generally irreversible in nature. Once coagulated or precipitated, they cannot be easily converted back into the colloidal state.

Why Other Options Are Incorrect:

The following are lyophilic colloids, which are usually reversible:

• A. Gelatin sol

• B. Starch sol

• C. Acacia sol

Lyophilic colloids can regain the colloidal state simply by adding the dispersion medium again.

GPAT Tip:

Remember:

• Type of Colloid Nature

• Lyophilic Reversible

• Lyophobic Irreversible

Common irreversible colloids:

• Ferric hydroxide sol

• Gold sol

• Arsenic sulfide sol

Irreversible colloid concept:

Lyophobic colloids = Irreversible nature

20. Association colloids are formed by:

A. Surfactant molecule aggregation.
B. Reduction reaction
C. Oxidation reaction
D. Polymerization

Answer: A

Explanation:

Association colloids are formed when surfactant molecules aggregate together in a solution at concentrations above the Critical Micelle Concentration (CMC) to form micelles.

These aggregates behave as colloidal particles.

Common examples:

• Soaps

• Detergents

• Sodium lauryl sulfate

In aqueous media:

• Hydrophobic tails aggregate inward

• Hydrophilic heads remain outward

Why Other Options Are Incorrect:

• B. Reduction reaction = Used in the preparation of some metallic sols

• C. Oxidation reaction = Used in the chemical preparation of colloids

• D. Polymerization = Formation of polymers, not association colloids

GPAT Tip:

Important relation:

Surfactants above CMC = Micelle formation

Association colloids are also called micellar colloids.

Micelle formation:

Surfactant molecules = Above CMC ​Micelles

21. The minimum concentration of surfactants to form micelles is:

A. CMC
B. Critical solution temperature
C. Kraft temperature
D. Colloidal Suspension

Answer: A

Explanation:

The Critical Micelle Concentration (CMC) is the minimum concentration of a surfactant required for the formation of micelles in solution.

• Below CMC = Surfactant molecules exist individually

• Above CMC = Surfactant molecules aggregate to form micelles

Micelle formation is important in:

• Solubilization

• Detergency

• Emulsification

• Drug delivery systems

Why Other Options Are Incorrect:

• B. Critical solution temperature → Temperature at which components become completely miscible

• C. Kraft temperature (Krafft temperature) → Minimum temperature required for micelle formation in ionic surfactants

• D. Colloidal suspension → Not a concentration term

GPAT Tip:

Do not confuse:

• Term Meaning

• CMC Minimum concentration for micelle formation

• Krafft temperature Minimum temperature for micelle formation

Micelle formation condition:

Surfactant concentration > CMC = Micelle formation

22. Which one shows maximum viscosity?

A. Lyophobic colloid
B. Lyophilic colloid
C. Suspension
D. Aerosol

Answer: B

Explanation:

Lyophilic colloids show comparatively higher viscosity because the dispersed particles have a strong affinity for the dispersion medium and become highly solvated (hydrated in water).

This solvation increases internal resistance to flow, thereby increasing viscosity.

Examples:

• Gelatin sol

• Starch sol

• Acacia sol

Why Other Options Are Incorrect:

• A. Lyophobic colloid → Viscosity is usually close to that of the dispersion medium

• C. Suspension → May settle and is not a true colloidal system

• D. Aerosol → Gas is the dispersion medium; viscosity is relatively low

GPAT Tip:

Important distinction:

• Property Lyophilic Colloid Lyophobic Colloid

• Affinity for solvent High Low

• Viscosity High Nearly the same as the solvent

• Stability High Low

Viscosity relation:

Higher solvation/hydration→Higher viscosity

23. What is the recommended method to purify colloids?

A. Sublimation
B. Distillation
C. Filtration
D. Dialysis

Answer: D

Explanation:

Dialysis is the commonly used method for the purification of colloidal dispersions. In this process, the colloidal solution is placed in a semipermeable membrane, which allows small ions and crystalloids to pass through while retaining the larger colloidal particles.

Thus, impurities such as electrolytes and small dissolved molecules are removed from the colloidal system.

Why Other Options Are Incorrect:

• A. Sublimation = Used for the purification of volatile solids

• B. Distillation = Used for the separation of liquids based on boiling point

• C. Filtration = Ordinary filter paper cannot effectively separate colloidal particles

GPAT Tip:

Remember:

• Method Purpose

• Dialysis: Purification of Colloids

• Electrodialysis: Faster dialysis using electric field

• Ultrafiltration: Separation using ultrafilters

Purification principle:

Small ions pass through a semipermeable membrane = Purified colloid

24. The movement that occurs in electro-osmosis:

A. Colloidal particles only
B. Ions only
C. Dispersion medium under an electric field
D. Dispersed particles only

Answer: C

Explanation:

Electro-osmosis is the movement of the dispersion medium through a porous material or capillary under the influence of an electric field, while the colloidal particles remain relatively stationary.

It occurs because the charged surface attracts ions from the medium, and when an electric field is applied, the liquid phase moves along with these ions.

Why Other Options Are Incorrect:

• A. Colloidal particles only = Describes electrophoresis

• B. Ions only = Not the complete definition of electro-osmosis

• D. Dispersed particles only = Again related to electrophoresis

GPAT Tip:

Differentiate clearly:

• Phenomenon What Moves?

• Electrophoresis Colloidal particles

• Electro-osmosis Dispersion medium

Electro-osmosis concept:

Electric field→Movement of dispersion medium

25. The protective colloid is used in pharmaceutical suspensions:

A. Gelatin
B. Hydrochloric acid
C. Potassium nitrate
D. Sodium chloride

Answer: B

Correct Answer: A. Gelatin

Explanation:

Gelatin acts as a protective colloid in pharmaceutical suspensions. Protective colloids stabilize lyophobic colloids by forming a protective layer around dispersed particles, preventing aggregation and coagulation.

Gelatin increases:

• Stability

• Viscosity

• Protection against electrolyte-induced coagulation

Why Other Options Are Incorrect:

• B. Hydrochloric acid = May destabilize colloids

• C. Potassium nitrate = Electrolyte; can promote coagulation

• D. Sodium chloride = Common coagulating electrolyte for colloids

GPAT Tip:

Common protective colloids:

• Gelatin

• Starch

• Acacia

• Gum tragacanth

Lower gold number = better protective colloid.

Protective action:

Protective colloid = Prevents coagulation of colloidal particles

26. The name of the optical property of colloids is used in nephelometry.

A. Light Refraction
B. Light Reflection
C. Light Scattering
D. Light Absorption

Answer: C

Explanation:

Nephelometry is based on the measurement of light scattering by colloidal particles suspended in a medium. When a beam of light passes through a colloidal system, the particles scatter the light in different directions due to the Tyndall effect.

The intensity of scattered light depends on:

• Particle size

• Particle concentration

• Wavelength of light

Why Other Options Are Incorrect:

• A. Light Refraction → Bending of light through media

• B. Light Reflection → Bouncing back of light from surfaces

• D. Light Absorption → Basis of colorimetry/spectrophotometry

GPAT Tip:

Remember the relation:

• Instrument Principle

• Nephelometer Measures scattered light

• Colorimeter Measures absorbed light

• Polarimeter Measures optical rotation

Nephelometry principle:

Scattered light intensity ∝ particle concentration

27. An electrolyte coagulation value is the

A. Minimum concentration required to coagulate a sol
B. Maximum amount required to coagulate a sol
C. Minimum amount required to stabilize a sol
D. Concentration needed for dialysis

Answer: A

Explanation:

The coagulation value of an electrolyte is defined as the minimum concentration of an electrolyte required to cause coagulation (precipitation) of a colloidal sol.

• Lower coagulation value → Greater coagulating power

• Higher coagulation value → Lower coagulating power

According to the Hardy–Schulze rule, ions with higher valency have stronger coagulating ability and therefore lower coagulation values.

Why Other Options Are Incorrect:

• B. Maximum amount required to coagulate a sol = Incorrect definition

• C. Minimum amount required to stabilize a sol = Related to protective colloids, not coagulation value

• D. Concentration needed for dialysis = Unrelated to coagulation value

GPAT Tip:

Important relation:

Coagulating power ∝ 1/Coagulation value

Thus:

• Low coagulation value = strong electrolyte for coagulation

Coagulation relation:

Coagulating power ∝ 1/Coagulation value

28. Which factor reduces Brownian movement?

A. Decreased particle size
B. Decreased kinetic energy
C. Increased viscosity
D. Increased temperature

Answer: C Increased viscosity

Explanation:

Brownian movement is the random zig-zag motion of colloidal particles caused by collisions with molecules of the dispersion medium.

An increase in the viscosity of the medium offers greater resistance to particle movement, thereby reducing Brownian motion.

Why Other Options Are Incorrect:

• A. Decreased particle size → Smaller particles show greater Brownian movement

• B. Decreased kinetic energy → Can reduce movement, but viscosity is the more direct and standard factor in colloidal systems

• D. Increased temperature → Increases kinetic energy and enhances Brownian movement

GPAT Tip:

Brownian motion:

• Increases with an increase in temperature

• Increases with a decrease in particle size

• Decreases with an increase in viscosity

Brownian movement relation:

Brownian motion ∝ Temperature/Viscosity

29. A colloidal dispersion has a liquid dispersed in another liquid, known as

A. Emulsion
B. Aerosol
C. Foam
D. Gel

Answer: A

Correct Answer: A. Emulsion

Explanation:

An emulsion is a colloidal system in which one liquid is dispersed in another immiscible liquid.

Types of emulsions:

• Oil-in-water (O/W) → Oil dispersed in water

• Water-in-oil (W/O) → Water dispersed in oil

Examples:

• Milk (O/W emulsion)

• Butter (W/O emulsion)

Why Other Options Are Incorrect:

• B. Aerosol → Solid or liquid dispersed in gas

• C. Foam → Gas dispersed in liquid or solid

• D. Gel → Liquid dispersed in a solid network

GPAT Tip:

Quick classification table:

• Dispersed Phase Dispersion Medium Type

• Liquid Liquid Emulsion

• Gas Liquid Foam

• Solid Liquid Sol

Emulsion concept:

Liquid dispersed in liquid = Emulsion

30. Which one is an example of an aerosol?

A. Smoke
B. Milk
C. Butter
D. Ghee

Answer: A

Correct Answer: A. Smoke

Explanation:

An aerosol is a colloidal system in which solid or liquid particles are dispersed in a gas.

Smoke is an example of a solid aerosol where tiny solid particles are dispersed in air.

Why Other Options Are Incorrect:

• B. Milk = Emulsion (liquid in liquid)

• C. Butter = Water-in-oil emulsion

• D. Ghee = Fatty material, not a colloidal aerosol

GPAT Tip:

Common aerosol examples:

• Type of Aerosol Example

• Solid in gas Smoke

• Liquid in gas Fog, mist, clouds

Aerosol classification:

Solid or liquid dispersed in gas = Aerosol

31. The lyophilic colloid's stability is due to

A. High density
B. High viscosity
C. Electrical charge only
D. Solvation and hydration

Answer: D. Solvation and hydration

Explanation:

The stability of lyophilic colloids is mainly due to solvation (or hydration in water). The solvent molecules surround the colloidal particles and form a protective layer, preventing aggregation and precipitation.

This solvated layer provides:

• High stability

• Reversible nature

• Resistance to coagulation

Why Other Options Are Incorrect:

• A. High density = Does not provide colloidal stability

• B. High viscosity = A property of lyophilic colloids, but not the main cause of stability

• C. Electrical charge only = More important in lyophobic colloids

GPAT Tip:

Remember:

• Colloid Type Main Cause of Stability

• Lyophilic Solvation/Hydration

• LyophobicElectrical charge

Lyophilic stability:

Solvation/Hydration layer = Colloidal stability

32. Which property differentiates colloids from true solutions?

A. Tyndall effect
B. Homogeneity
C. Transparency
D. Small molecular size

Answer: A. Tyndall effect

Explanation:

The Tyndall effect is the scattering of light by colloidal particles and is the main property that differentiates colloids from true solutions.

• Colloids = Show the Tyndall effect because their particles are large enough to scatter light.

• True solutions = Do not show Tyndall effect because solute particles are too small to scatter light.

Why Other Options Are Incorrect:

• B. Homogeneity → True solutions are homogeneous; colloids appear homogeneous but are actually heterogeneous

• C. Transparency → Both may appear transparent or translucent

• D. Small molecular size → Characteristic of true solutions, not colloids

GPAT Tip:

Quick comparison:

• Property True Solution Colloid

• Particle size < 1 nm 1–1000 nm

• Tyndall effect Absent Present

• Visibility under ultramicroscope No Yes

Key concept:

Colloidal particles + Light = Tyndall effect

33. Which colloidal system is used in intravenous drug delivery/diagnostic imaging?

A. Liposomes
B. Suspensions
C. Emulsion
D. Dry powder injection

Answer: A. Liposomes

Explanation:

Liposomes are colloidal vesicular systems widely used in:

• Intravenous drug delivery

• Targeted drug delivery

• Diagnostic imaging

• Controlled release formulations

They consist of phospholipid bilayers capable of entrapping both:

• Hydrophilic drugs (inside aqueous core)

• Lipophilic drugs (within lipid bilayer)

Liposomes improve:

• Drug targeting

• Bioavailability

• Reduced toxicity

Why Other Options Are Incorrect:

• B. Suspensions = Not primarily used for diagnostic imaging or targeted IV colloidal delivery

• C. Emulsion = Some emulsions are injectable, but liposomes are more specific for advanced IV delivery and imaging

• D. Dry powder injection = Not a colloidal delivery system

GPAT Tip:

Important colloidal carriers in pharmaceutics:

• Carrier Application

• Liposomes Targeted IV Drug Delivery

• Nanoparticles Controlled release

• Micelles Solubilization

Liposome structure:

Phospholipid bilayer = Drug encapsulation and targeted delivery

34. The movement of particles in a colloidal system towards an oppositely charged electrode is called:

A. Electrophoresis
B. Peptization
C. Osmosis
D. Dialysis

Answer: A. Electrophoresis

Explanation:

Electrophoresis is the movement of charged colloidal particles toward the oppositely charged electrode under the influence of an electric field.

• Positively charged particles move toward the cathode.

• Negatively charged particles move toward the anode.

This phenomenon helps determine:

• Nature of charge on colloidal particles

• Stability of colloidal systems

Why Other Options Are Incorrect:

• B. Peptization = Conversion of precipitate into colloidal sol

• C. Osmosis = Movement of solvent through a semipermeable membrane

• D. Dialysis = Purification of colloids by removing small ions

GPAT Tip:

Differentiate these terms carefully:

• Process Definition

• Electrophoresis Movement of colloidal particles

• Electro-osmosis Movement of dispersion medium

• Dialysis Purification through membrane

Electrophoresis process:

Charged particles+Electric field→Migration toward opposite electrode

35. Which ONE acts as a protective colloid?

A. Ferric chloride
B. Potassium chloride
C. Sodium sulfate
D. Acacia

Answer: D. Acacia

Explanation:

Acacia is a lyophilic colloid that acts as a protective colloid by stabilizing lyophobic colloidal systems. It forms a protective layer around colloidal particles and prevents their coagulation.

Protective colloids improve:

• Stability

• Resistance to electrolytes

• Shelf life of suspensions and emulsions

Why Other Options Are Incorrect:

• A. Ferric chloride = Electrolyte; may cause coagulation

• B. Potassium chloride = Electrolyte, not a protective colloid

• C. Sodium sulfate = Electrolyte that can destabilize colloids

GPAT Tip:

Common protective colloids:

• Acacia

• Gelatin

• Starch

• Tragacanth

Protective action:

Protective colloid = Prevents coagulation and stabilizes colloids

36. The coagulating power of cations for negative sols is in the following order:

A. Ba²⁺ > Na⁺ > Al³⁺
B. Na⁺ > Al³⁺ > Ba²⁺
C. Na⁺ > Ba²⁺ > Al³⁺
D. Al³⁺ > Ba²⁺ > Na⁺

Answer: D. Al³⁺ > Ba²⁺ > Na⁺

Explanation:

According to the Hardy–Schulze rule, the coagulating power of an ion increases with the valency of the ion carrying charge opposite to the colloidal particles.

For a negatively charged sol, the active coagulating ions are cations.

Valencies:

• Al³⁺ = 3+

• Ba²⁺ = 2+

• Na⁺ = 1+

Hence, coagulating power follows the following:

Al3+>Ba2+>Na+

GPAT Tip:

Remember:

Higher valency = Higher coagulating power = Lower coagulation value

For negatively charged sols:

3+>2+>1+

Hardy–Schulze rule:

Coagulating power ∝ Valency of oppositely charged ion

37. Which preparation exhibits colloidal behavior?

A. Elixir
B. Liposomal drug delivery system
C. Nanoparticles
D. Tincture

Answer: B. Liposomal drug delivery system

Explanation:

A liposomal drug delivery system exhibits clear colloidal behavior because liposomes are microscopic vesicular colloidal carriers composed of phospholipid bilayers dispersed in a medium.

They are widely used for:

• Targeted drug delivery

• Intravenous formulations

• Controlled release

• Diagnostic imaging

Why Other Options Are Incorrect:

• A. Elixir: Clear hydroalcoholic solution, not colloidal

• C. Nanoparticles: Also show colloidal behavior, but liposomal systems are the classic pharmaceutical colloidal preparation expected in such MCQs

• D. Tincture: Alcoholic solution of plant or chemical substances

GPAT Tip:

Common pharmaceutical colloidal systems:

• Liposomes

• Micelles

• Nanoemulsions

• Nanoparticles

Liposomal system:

Phospholipid vesicles dispersed in medium = Colloidal system

38. The settling of colloidal particles is prevented due to:

A. Osmosis
B. Diffraction
C. Interfacial tension
D. Brownian movement

Answer: D. Brownian movement

Explanation:

Brownian movement is the continuous random zig-zag motion of colloidal particles caused by collisions with molecules of the dispersion medium. This constant movement prevents the particles from settling under gravity.

Thus, Brownian movement plays an important role in maintaining the stability of colloidal dispersions.

Why Other Options Are Incorrect:

• A. Osmosis: Movement of solvent through semipermeable membrane

• B. Diffraction: Bending/spreading of waves around obstacles

• C. Interfacial tension: Surface phenomenon, not responsible for preventing settling

GPAT Tip:

Important role of Brownian motion:

• Prevents sedimentation

• Enhances diffusion

• Maintains uniform dispersion

Brownian movement effect:

Continuous random motion → Prevention of particle settling

39. Which one is NOT a kinetic property of colloids?

A. Diffusion
B. Brownian movement
C. Osmotic pressure
D. Electrophoresis

Answer: D. Electrophoresis

Explanation:

Kinetic properties of colloids are related to the movement of colloidal particles. These include:

• Diffusion

• Brownian movement

• Osmotic pressure

Electrophoresis is considered an electrical property, not a kinetic property, because it involves the movement of charged particles under an applied electric field.

Why Other Options Are Incorrect:

• A. Diffusion: Kinetic property due to particle motion

• B. Brownian movement: Important kinetic property

• C. Osmotic pressure: Related to the movement and distribution of particles

GPAT Tip:

Classification frequently asked in GPAT:

• Property Type Examples

• Kinetic properties Brownian motion, diffusion, osmotic pressure

• Optical properties Tyndall effect

• Electrical properties Electrophoresis, electro-osmosis

Property classification:

Electrophoresis = Electrical property of colloids

40. The pharmaceutical application of colloids includes:

A. Diagnostic agents
B. Plasma expanders
C. Controlled drug delivery
D. All of the above

Answer: D. All of the above

Explanation:

Colloidal systems have numerous pharmaceutical applications due to their unique particle size and surface properties.

Applications include:

• Diagnostic agents. Example: Radioactive colloids used in imaging and diagnostic procedures.

• Plasma expanders. Example: Dextran solutions are used to maintain blood volume.

• Controlled drug delivery. Colloidal carriers such as liposomes, nanoparticles, and micelles improve targeted and sustained drug release.

GPAT Tip:

Important pharmaceutical applications of colloids are frequently asked in GPAT:

• Application Example

• Plasma expander: Dextran

• Drug delivery: Liposomes, nanoparticles

• Diagnostics: Radioactive colloids

Drug delivery concept:

Colloidal carriers = Targeted and controlled drug delivery

Dr. Alok Singh