In colloidal chemistry, understanding the structure of a colloid is essential for grasping how colloidal systems behave. The two fundamental components of any colloidal system are the disperse phase and dispersion medium. A clear understanding of disperse phase and dispersion medium helps aspirants explain the nature, classification, and applications of colloids in chemistry, biology, medicine, and industry.

A colloid is a heterogeneous mixture in which very small particles of one substance are uniformly distributed throughout another substance. These two components are known as the disperse phase and dispersion medium, and their interaction determines the properties of the colloidal system.

Definition of Disperse Phase

The disperse phase is the substance that is present in a small amount and is scattered in the form of tiny particles throughout another substance. These particles usually have sizes ranging from 1 nm to 1000 nm. In any colloid, identifying the disperse phase and dispersion medium is the first step toward classifying the system.

For example, in milk, fat globules act as the disperse phase. Similarly, in smoke, solid carbon particles represent the disperse phase. In both cases, the behavior of the system depends on the nature of the disperse phase and dispersion medium.

Definition of Dispersion Medium

The dispersion medium is the substance present in a larger amount and serves as the continuous phase in which the disperse phase particles are distributed. The dispersion medium can be solid, liquid, or gas. The relationship between the disperse phase and dispersion medium determines whether the colloid is a sol, gel, emulsion, foam, or aerosol.

For instance, in milk, water is the dispersion medium. In fog, air acts as the dispersion medium. These examples clearly illustrate the importance of understanding disperse phase and dispersion medium.

Classification of Colloids Based on Physical State

One of the most important applications of disperse phase and dispersion medium is the classification of colloids. Colloids are categorized based on the physical states of the disperse phase and dispersion medium.

• Sol: Solid dispersed in liquid (e.g., paint)

• Emulsion: Liquid dispersed in liquid (e.g., milk)

• Foam: Gas dispersed in liquid (e.g., shaving cream)

• Aerosol: Solid or liquid dispersed in gas (e.g., smoke, fog)

• Gel: Liquid dispersed in solid (e.g., jelly)

Each of these systems is defined by a specific combination of disperse phase and dispersion medium.

Role in Stability of Colloids

The stability of a colloidal system depends strongly on the interaction between the disperse phase and dispersion medium. Factors such as charge on colloidal particles, solvation, and the presence of electrolytes influence how the disperse phase remains suspended in the dispersion medium.

Protective colloids, for example, enhance stability by forming a protective layer around the disperse phase. This concept again highlights the importance of disperse phase and dispersion medium in real systems.

Examples from Daily Life

Many everyday substances are colloids, and recognizing the disperse phase and dispersion medium helps explain their properties. Butter is a colloid in which water is the disperse phase and fat is the dispersion medium. Ink consists of solid dye particles as the disperse phase in a liquid dispersion medium.

Even biological fluids such as blood are colloidal systems, where cells act as the disperse phase and plasma is the dispersion medium. These real-life examples show how disperse phase and dispersion medium are relevant beyond textbooks.

Importance in Industry and Science

Industrial products like paints, cosmetics, medicines, and food items rely on carefully controlled disperse phase and dispersion medium combinations. In pharmaceuticals, drug particles are often the disperse phase to ensure proper absorption. In environmental chemistry, aerosols are studied by analyzing their disperse phase and dispersion medium.

 30 MCQs on Disperse Phase and Dispersion Medium:

1.

The volume of CO₂ formed at STP on burning a mixture of 0.5 mole of methane and 24 g of oxygen is:

A. 4.4 litre
B. 8.4 litre
C. 22.4 litre
D. 0.84 litre

Answer: B

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2.

How many grams of NaOH will be required to prepare 500 gram solution containing 10% w/w NaOH solution?

A. 50 grams
B. 0.5 grams
C. 10 grams
D. 100 grams

Answer: A

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3.

Molarity is expressed as:

A. Litre/mole
B. Moles/litre
C. Moles/1000 gms
D. Grams/litre

Answer: B

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4.

10.6 g of a substance of molecular weight 106 was dissolved in 100 mL. 10 mL of this solution was diluted to 1000 mL. The molarity of resulting solution is:

A. 1.0 M
B. 10⁻¹ M
C. 10⁻² M
D. 10⁻³ M

Answer: C

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5.

Weight (in gram) of KCl (mol wt = 74.5) in 100 mL of 0.1 M KCl solution is:

A. 7.45 g
B. 0.745 g
C. 0.0745 g
D. 74.5 g

Answer: B

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6.

5.85 g NaCl (mol wt 58.5) is dissolved and solution is made up to 500 mL. Molarity is:

A. 0.1
B. 0.2
C. 1
D. 0.117

Answer: B

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7.

If 20 mL of 0.4 N NaOH neutralizes 40 mL of a dibasic acid, molarity of acid is:

A. 0.1 M
B. 0.2 M
C. 0.3 M
D. 0.4 M

 Answer: A

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8.

9.8 g of H₂SO₄ is present in 2 litres of solution. Molarity is:

A. 0.1 M
B. 0.05 M
C. 0.01 M
D. 0.2 M

Answer: B

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9.

Weight of oxalic acid crystals H₂C₂O₄·2H₂O required to prepare 500 mL of 0.2 N solution is:

A. 3.15 g
B. 6.3 g
C. 12.6 g
D. 126 g

 Answer: B

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10.

138 g ethyl alcohol is mixed with 72 g water. Ratio of mole fraction of alcohol to water is:

A. (3 : 4)
B. (1 : 2)
C. (1 : 4)
D. (1 : 1)

Answer: A

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11.

Equal masses of hydrogen gas and oxygen gas are placed in a closed container at pressure 3.4 atm. Contribution of hydrogen gas is:

A. 1.7 atm
B. 0.2 atm
C. 3.2 atm
D. 3.02 atm

 Answer: C

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12.

Volumes of 10 N and 4 N HCl required to make 1 L of 7 N HCl are:

A. 0.50 L of 10 N and 0.50 L of 4 N
B. 0.60 L of 10 N and 0.40 L of 4 N
C. 0.80 L of 10 N and 0.20 L of 4 N
D. 0.75 L of 10 N and 0.25 L of 4 N

 Answer: A

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13.

When a sulphur sol is evaporated, sulphur is obtained. On mixing with water, sulphur sol is not formed. The sol is:

A. Lyophilic
B. Reversible
C. Hydrophobic
D. Hydrophilic

 Answer: C

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14.

4.5 g of aluminium is deposited from Al³⁺ by certain charge. Volume of hydrogen produced at STP by same charge is:

A. 22.4 L
B. 44.8 L
C. 11.2 L
D. 5.6 L

 Answer: D

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15.

Mass of carbon anode consumed (forming only CO₂) to produce 270 kg aluminium in Hall process is:

A. 180 kg
B. 270 kg
C. 540 kg
D. 90 kg

Answer: D

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16.

The molarity of solution obtained by dissolving 2.5 g NaCl in 100 mL water is:

A. 0.0427 moles
B. 0.427 moles
C. 0.00427 moles
D. 0.027 moles

 Answer: B

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17.

One part of solute in one million parts of solvent is expressed as:

A. ppm
B. mg/100 cc
C. g/L
D. g/100 cc

Answer: A

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18.

On mixing ethyl acetate with aqueous NaCl, the composition is:

A. CH₃COOC₂H₅ + NaCl
B. CH₃COONa + CH₃OH
C. CH₃COOH + CH₃OH + NaOH
D. CH₃CH₂CH₂COONa

 Answer: A

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19.

Density (g mL⁻¹) of 3.60 M H₂SO₄ solution which is 29% by mass is:

A. 1.64
B. 1.88
C. 1.22
D. 1.45

Answer: C

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20.

Equal masses of methane and oxygen mixed. Fraction of total pressure exerted by oxygen is:

A. 2/3
B. (1/2) × (273/298)
C. 1/3
D. 1/2

 Answer: C

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21.

Mixture of ethyl alcohol and propyl alcohol has vapour pressure 290 mm at 300 K. Vapour pressure of propyl alcohol = 200 mm. Mole fraction of ethyl alcohol = 0.6. Vapour pressure of ethyl alcohol is:

A. 300
B. 700
C. 360
D. 350

Answer: D

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22.

Volume strength of 1.5 N H₂O₂ solution is:

A. 8.4
B. 4.8
C. 5.2
D. 8.8

Answer: A

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23.

Dispersed phase and dispersion medium in butter are respectively:

A. solid and liquid
B. liquid and solid
C. liquid and liquid
D. solid and solid

Answer: B

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24.

Aqueous glucose solution is 20% in strength. Volume in which 1 g-mole is dissolved will be:

A. 8 L
B. 1.8 L
C. 9 L
D. 0.9 L

 Answer: D

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25.

Volume of water to be added to 100 cm³ of 0.5 N H₂SO₄ to get decinormal concentration is:

A. 400 cm³
B. 450 cm³
C. 500 cm³
D. 100 cm³

 Answer: A

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26.

Which concentration terms are independent of temperature?

A. Molarity
B. Molarity and mole fraction
C. Mole fraction and molality
D. Molality and normality

 Answer: C

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27.

5 litres solution contains 25 mg CaCO₃. Concentration in ppm is:

A. 5
B. 1
C. 25
D. 0.5

 Answer: A

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28.

Density of 2.05 M acetic acid solution is 1.02 g/mL. Molality is:

A. 1.14 mol kg⁻¹
B. 3.28 mol kg⁻¹
C. 2.28 mol kg⁻¹
D. 0.44 mol kg⁻¹

Answer: C

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29.

Acidified KMnO₄ oxidizes oxalic acid. Volume of 10⁻⁴ M KMnO₄ required to oxidize 0.5 L of 10⁻² M oxalic acid is:

A. 25
B. 1250
C. 20
D. 2

 Answer: C

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30.

Pentane : Hexane mole ratio = 1 : 4. Vapour pressures are 440 mm and 120 mm. Mole fraction of pentane in vapour phase is:

A. 0.2
B. 0.549
C. 0.786
D. 0.478

Answer: D

Conclusion on Disperse Phase and Dispersion Medium

In conclusion, disperse phase and dispersion medium are the foundation of colloidal chemistry. Every colloidal system is defined by these two components, and their interaction governs classification, stability, and applications. From milk and smoke to medicines and industrial products, understanding disperse phase and dispersion medium allows students to connect theoretical chemistry with real-world phenomena. Mastery of disperse phase and dispersion medium is essential for success in physical chemistry topics and competitive examinations such as NEET, JEE, and CUET.