1. What is latex in the context of rubber colloids?
A.
A colloidal dispersion of rubber in water
B.
A true solution of rubber in water
C.
A suspension of salt in rubber
D.
A gaseous mixture of rubber vapour and air
Correct Answer:
A colloidal dispersion of rubber in water
Explanation:
Latex is a rubber colloid in which tiny rubber particles are dispersed throughout water.
2. In natural latex, rubber particles are dispersed in which medium?
A.
Alcohol
B.
Water
C.
Benzene
D.
Ether
Correct Answer:
Water
Explanation:
Natural latex is a colloidal system with rubber as the dispersed phase and water as the dispersion medium.
3. What type of colloidal system is natural latex?
A.
A sol
B.
A foam
C.
An aerosol
D.
A gel
Correct Answer:
A sol
Explanation:
Latex is called a sol because solid rubber particles are dispersed in a liquid medium, water.
4. What is the usual charge on rubber particles in natural latex?
A.
Positive charge
B.
Negative charge
C.
No charge
D.
Alternating positive and negative charges
Correct Answer:
Negative charge
Explanation:
Rubber particles in latex generally carry negative charges, which help them remain dispersed by mutual repulsion.
5. Why do rubber particles in latex remain dispersed for some time?
A.
They attract each other strongly
B.
Their similar charges cause mutual repulsion
C.
They evaporate continuously
D.
They dissolve completely in water
Correct Answer:
Their similar charges cause mutual repulsion
Explanation:
The similarly charged rubber particles repel one another, helping to prevent their immediate aggregation.
6. Which process converts latex into solid rubber by removing the colloidal stability?
A.
Coagulation
B.
Distillation
C.
Sublimation
D.
Crystallisation
Correct Answer:
Coagulation
Explanation:
Coagulation causes the rubber particles in latex to come together and separate as solid rubber.
7. Which substance is commonly used to coagulate natural rubber latex?
A.
Acetic acid
B.
Sodium chloride solution only
C.
Distilled water
D.
Liquid ammonia
Correct Answer:
Acetic acid
Explanation:
Acetic acid neutralizes the charge responsible for the stability of rubber particles and causes latex to coagulate.
8. What happens when an acid is added to natural latex?
A.
Rubber particles coagulate
B.
Rubber particles become a gas
C.
Rubber dissolves completely in water
D.
The latex changes into a foam
Correct Answer:
Rubber particles coagulate
Explanation:
Acid reduces the electrostatic repulsion between rubber particles, allowing them to aggregate and form coagulated rubber.
9. Which substance is added to latex to help preserve its colloidal stability?
A.
Ammonia
B.
Acetic acid
C.
Formic acid
D.
Hydrochloric acid
Correct Answer:
Ammonia
Explanation:
A small amount of ammonia helps prevent premature coagulation and keeps the rubber particles dispersed in latex.
10. What is the dispersed phase in a rubber colloid such as latex?
A.
Water
B.
Rubber particles
C.
Ammonia gas
D.
Acetic acid
Correct Answer:
Rubber particles
Explanation:
In latex, rubber particles form the dispersed phase, while water acts as the dispersion medium.
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