Chemistry Questions and Answers – Surface Chemistry – Colloids Classification

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This set of Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Surface Chemistry – Colloids Classification”.

1. Colloids are classified into lyophobic and lyophilic colloids.
a) True
b) False
View Answer

Answer: a
Explanation: Based on the interaction between the dispersed and dispersion medium, colloids are classified into two types, lyophilic and lyophobic colloids. Lyophilic colloids are those in which the dispersed phase has high affinity for dispersion medium and lyophobic colloids are those in which the dispersed phase has no affinity or least affinity for the dispersion medium.
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2. Which of the following is not an example of lyophilic colloids?
a) Starch solution
b) Gelatin
c) Gum
d) Silver solution
View Answer

Answer: d
Explanation: Starch solution, gelatin and gum are colloids in which the dispersed phase has very high affinity for the dispersion medium and therefore they are categorized as lyophilic colloids. Silver solution on the other hand is an example of lyophobic colloids.

3. Which of the following is not an example of lyophobic colloids?
a) Gold solution
b) Sulphur solution
c) NaCl solution
d) Blood
View Answer

Answer: c
Explanation: Gold solution, Sulphur solution and blood are colloids in which the dispersed phase has very low affinity for the dispersion medium and once the dispersed phase and dispersion medium are separated we cannot get the solution directly by remixing the two phases. Therefore they are categorized under lyophobic colloids.
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4. Colloids are classified into multi-molecular, macro-molecular and associated colloids.
a) True
b) False
View Answer

Answer: a
Explanation: Based on the nature of dispersed phase, colloids are classified into multi-molecular, macro-molecular and associated colloids. In multi-molecular colloids a large number of atoms aggregate to form a particle of colloidal size, in macro-molecular colloids molecules dissolve in suitable solvents and give rise to particles of colloidal size. Colloids which behave as a normal strong electrolyte at low concentration but exhibits colloidal properties at higher concentration are known as associated colloids.

5. Which of the following is a characteristic of a multi-molecular colloid?
a) Large number of molecules combine to form a particle of colloidal size
b) A large number of atoms aggregate to form a particle of colloidal size
c) Starch solution is an example of multi-molecular colloid
d) Multi-molecular colloids are normally of the lyophilic type
View Answer

Answer: b
Explanation: In this type of colloidal solution, a large number of atoms or small molecules aggregate to form a particle of colloidal size, these are normally of lyophobic type. Starch solution is an example of lyophilic colloids and hence is not an example for multi-molecular colloids.
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6. Which of the following is false regarding macro-molecular colloids?
a) Protein solution is an example for macro-molecular colloids
b) Man-made macro-molecules like polythene can form such colloids
c) Silver solution can form macro-molecular colloids
d) These are normally of lyophilic type
View Answer

Answer: c
Explanation: Macro-molecules dissolve in a suitable solvents, gives rise to particles of colloidal size. These are normally of lyophilic type and silver solution is an example for lyophobic and multi-molecular colloids.

7. Which of the following is not an example of associated colloids?
a) Sodium stearate
b) Potassium stearate
c) Gum
d) Detergents
View Answer

Answer: c
Explanation: Some substances at low concentration behave as true solutions. As the concentration of the solution increases, it turns to be a colloidal solution. These type of colloids are knows as associated solution. Soaps like sodium stearate potassium stearate and detergents are examples of associated colloids whereas gum is an example for lyophilic colloids.
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8. Which of the following colloids cannot be formed by direct mixing?
a) Lyophilic colloids
b) Lyophobic colloids
c) Macro-molecular colloids
d) Associated colloids
View Answer

Answer: b
Explanation: Lyophobic colloids such as metal solutions like gold and silver solution, sulphur solution and blood cannot be prepared directly by mixing. These are prepared by special methods and are irreversible in nature. Once the dispersed phase and medium are separated it is not possible to get the solution by remixing the two phases.

9. Which of the following colloids is most stable?
a) Starch solution
b) Blood
c) Sulphur solution
d) Silver solution
View Answer

Answer: a
Explanation: Starch solution is most stable among the following because it is a lyophilic colloid and the solutions are highly stable due to the high interaction between the dispersed phase and the dispersion medium.
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10. In which of the following, the dispersed phase and medium can be separated by evaporation?
a) Ferric hydroxide solution
b) Sulphur solution
c) Metal in water
d) Starch solution
View Answer

Answer: d
Explanation: In starch solution, if the dispersed phase and the dispersion medium are separated by evaporation, the colloidal solution can be regained by remixing the dispersed phase and dispersion medium. Hence these are called reversible solutions are highly stable because of the high interaction between the dispersed phase and medium.

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