Engineering Chemistry MCQ (Micelles)

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Engineering Chemistry MCQ (Micelles)

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1. What is the molecular formula of stearate ion?
a) C17H35COO–
b) C35H17COO+
c) C35H17COO–
d) C17H35COO+
Answer: a
Explanation: Sodium stearate ionises to form stearate anion(C17H35COO– ) and sodium cation(Na+).

2. Which part of the stearate ion is hydrophilic in nature?
a) Tail
b) Hydrocarbon chain
c) Head
d) None of the mentioned
Answer: c
Explanation: The end of the hydrocarbon chain is having a polar group (head) which
is hydrophilic in nature and represented by a hollow circle.

3. Which of the following is water insoluble?
a) COO–
b) Na+
c) C17H35
d) All of the mentioned
Answer: b
Explanation: C17H35 is hydrophobic in nature and hence it is water insoluble.

4. The number of stearate ions required to form a micelle of colloidal size is ___________
a) 50
b) 60
c) 70
d) 80
Answer: c
Explanation: About 70 stearate ions aggregate to form a micelle of colloidal size.

5. Select the incorrect statement from the following options.
a) In the micelle formation, the water soluble heads are directed towards the centre
b) In the micelle formation, the water soluble heads are on the surface in contact with the water
c) In the micelle formation, the water insoluble tails are directed towards the centre
d) None of the mentioned
Answer: a
Explanation: In the micelle formation, the water insoluble tails are directed towards
the centre, and the water soluble heads are on the surface in contact with water. All the other options are correct.

6. Select the correct statement from the following options.
a) The soap micelle is unstable due to positive charge on its head
b) The soap micelle is stable due to positive charge on its head
c) The soap micelle is unstable due to negative charge on its head
d) The soap micelle is stable due to negative charge on its head
Answer: d
Explanation: The soap micelle is stable due to the negative charge on its polar head.
In the micelle formation, the water insoluble tails are directed towards the centre,
and the water soluble heads are on the surface in contact with water.

7. The transition of ions to micelle is ___________
a) Reversible
b) Irreversible
c) All of the mentioned
d) None of the mentioned
Answer: a
Explanation: The transition of ions to micelle is a reversible process. In the micelle
formation, the water insoluble tails are directed towards the centre, and the water
soluble heads are on the surface in contact with water.

8. What is Critical Micelle Concentration?
a) The maximum amount of concentration that is required for the formation of micelle
b) The minimum amount of concentration that is required for the formation of micelle
c) The maximum amount of concentration that is not required for the formation of micelle
d) The minimum amount of concentration that is not required for the formation of micelle
Answer: b
Explanation: The minimum amount of concentration that is required for the
formation of the micelle is termed as Critical Micelle Concentration (CMC). It is
defined as the concentration of surfactants above which micelles form and all
additional surfactants added to the system go to micelles.

9. Micelles behave as colloids only when?
a) Concentration is less than CMC
b) Concentration is equal to CMC
c) Concentration is greater than CMC
d) They always behave as colloids
Answer: c
Explanation: Micelles behave as colloids only when its concentration is greater than
CMC. The CMC is an important characteristic of a surfactant. Before reaching the
CMC, the surface tension changes strongly with the concentration of the surfactant.
After reaching the CMC, the surface tension remains relatively constant or changes with a lower slope.

10. The conductivity of micelles is ___________
a) Higher than a colloidal solution
b) Lower than a colloidal solution
c) Equals to colloidal solution
d) None of the mentioned
Answer: a
Explanation: The conductivity of micelles is higher than the colloidal solution. And
hence they can conduct more electric charges through them.