1. When starch is dispersed in hot water, it generally forms a:
A.
Starch sol
B.
True solution of sodium chloride
C.
Suspension of sand
D.
Metallic sol
Correct Answer:
Starch sol
Explanation:
Starch forms a colloidal dispersion, called a starch sol, when dispersed in hot water.
2. Starch colloids are classified as macromolecular colloids because starch molecules:
A.
Have very small atomic masses
B.
Are large polymeric molecules
C.
Are simple ions
D.
Are metallic particles
Correct Answer:
Are large polymeric molecules
Explanation:
Starch consists of very large polymeric molecules, so its colloidal particles behave as macromolecular colloids.
3. The affinity of starch for water makes starch colloids generally:
A.
Lyophilic
B.
Lyophobic
C.
Metallic
D.
Gaseous
Correct Answer:
Lyophilic
Explanation:
Starch has a strong affinity for water; therefore, starch-water colloids are lyophilic colloids.
4. A starch colloid in water is best described as a:
A.
Hydrosol
B.
Aerosol
C.
Foam
D.
Gelatinous precipitate only
Correct Answer:
Hydrosol
Explanation:
A colloidal dispersion of starch in water is called a hydrosol because water acts as the dispersion medium.
5. Starch colloids can show the Tyndall effect because they:
A.
Scatter a beam of light
B.
Absorb all incident light
C.
Convert light into sound
D.
Contain only dissolved ions
Correct Answer:
Scatter a beam of light
Explanation:
Starch colloidal particles are large enough to scatter light, producing the Tyndall effect.
6. The dispersion medium in a starch sol prepared with water is:
A.
Starch
B.
Water
C.
Oxygen
D.
Ethanol vapor
Correct Answer:
Water
Explanation:
In a starch sol, starch is the dispersed substance and water is the continuous dispersion medium.
7. On cooling a concentrated starch sol, it may form a:
A.
Starch gel
B.
Metallic crystal
C.
Gas mixture
D.
True ionic solution
Correct Answer:
Starch gel
Explanation:
A concentrated starch sol can set into a semisolid starch gel on cooling.
8. Which property is characteristic of starch as a macromolecular colloid?
A.
It consists of very large molecules dispersed in a medium
B.
It consists only of free electrons
C.
It is always a gas dispersed in a liquid
D.
It contains no polymeric material
Correct Answer:
It consists of very large molecules dispersed in a medium
Explanation:
Macromolecular colloids such as starch contain large polymer molecules dispersed in a suitable medium.
9. Starch colloids are usually prepared by dispersing starch in:
A.
Hot water
B.
Liquid mercury
C.
Molten iron
D.
Dry oxygen
Correct Answer:
Hot water
Explanation:
Starch is commonly dispersed in hot water to form a starch colloid or starch sol.
10. Compared with a true solution, a starch colloid has particles that are:
A.
Larger and capable of scattering light
B.
Smaller than individual atoms
C.
Always visible as large solid pieces
D.
Absent from the dispersion
Correct Answer:
Larger and capable of scattering light
Explanation:
Starch colloidal particles are larger than solute particles in a true solution and can scatter light.
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