Practice important
Protective Action
MCQ questions and answers.
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10
MCQ Questions
1. What is the main function of a protective colloid?
A.
To increase the size of colloidal particles
B.
To prevent the coagulation of a lyophobic sol
C.
To convert a sol into a true solution
D.
To remove the dispersion medium
Correct Answer:
To prevent the coagulation of a lyophobic sol
Explanation:
A protective colloid forms a protective layer around the particles of a lyophobic sol and prevents their coagulation.
2. Which type of colloid generally acts as a protective colloid?
A.
Lyophilic colloid
B.
Lyophobic colloid
C.
Suspension
D.
True solution
Correct Answer:
Lyophilic colloid
Explanation:
Lyophilic colloids have a strong affinity for the dispersion medium and can protect lyophobic colloidal particles from coagulation.
3. Which of the following can act as a protective colloid for a gold sol?
A.
Gelatin
B.
Sodium chloride
C.
Hydrochloric acid
D.
Potassium nitrate
Correct Answer:
Gelatin
Explanation:
Gelatin is a lyophilic colloid that can surround gold sol particles and protect them from coagulation by electrolytes.
4. Protective action occurs mainly because the protective colloid:
A.
Forms a layer around the colloidal particles
B.
Destroys the dispersion medium
C.
Changes the particles into ions
D.
Removes all ions from the sol
Correct Answer:
Forms a layer around the colloidal particles
Explanation:
The protective colloid gets adsorbed on the surface of the dispersed particles and forms a stabilizing layer around them.
5. The protective power of a colloid is commonly measured by its:
A.
Gold number
B.
pH value
C.
Boiling point
D.
Molecular volume
Correct Answer:
Gold number
Explanation:
Gold number is used to compare the protective power of different colloids in protecting a gold sol from coagulation.
6. A protective colloid with a lower gold number has:
A.
Greater protective power
B.
Lower protective power
C.
No protective action
D.
Greater tendency to coagulate itself
Correct Answer:
Greater protective power
Explanation:
A lower gold number means that a smaller mass of the protective colloid is required to prevent coagulation, so its protective power is greater.
7. Which substance is commonly used as a protective colloid because it is a lyophilic colloid?
A.
Starch
B.
Sodium chloride
C.
Potassium chloride
D.
Calcium nitrate
Correct Answer:
Starch
Explanation:
Starch is a lyophilic colloid and can protect lyophobic sols by forming a hydrated layer around their particles.
8. In the gold number test, the protective colloid prevents the coagulation of:
A.
Gold sol
B.
Sugar solution
C.
Sodium chloride solution
D.
Distilled water
Correct Answer:
Gold sol
Explanation:
The gold number measures the amount of protective colloid needed to protect a standard gold sol from coagulation by an electrolyte.
9. Which of the following has the greatest protective action if its gold number is the lowest?
A.
Colloid X with gold number 2
B.
Colloid Y with gold number 5
C.
Colloid Z with gold number 8
D.
Colloid W with gold number 10
Correct Answer:
Colloid X with gold number 2
Explanation:
The lower the gold number, the greater the protective action. Therefore, colloid X has the greatest protective power.
10. Which of the following is an example of a protective colloid used to stabilize a lyophobic sol?
A.
Gum arabic
B.
Sodium chloride
C.
Potassium sulphate
D.
Calcium chloride
Correct Answer:
Gum arabic
Explanation:
Gum arabic is a lyophilic colloid that protects lyophobic sols by forming a protective film around their dispersed particles.
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Protective Action
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