Practice important
Gelatin Imbibition
MCQ questions and answers.
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10
MCQ Questions
1. When a dry gelatin strip is placed in water, its increase in volume is primarily caused by which process?
A.
Adsorption of water by hydrophilic groups in the gelatin network
B.
Active transport of water through living gelatin cells
C.
Osmosis across a selectively permeable gelatin membrane
D.
Conversion of gelatin molecules into soluble ions
Correct Answer:
Adsorption of water by hydrophilic groups in the gelatin network
Explanation:
Gelatin is a hydrophilic colloid. Its polar groups attract and hold water on the surface and within the spaces of its molecular network, producing imbibition and swelling.
2. Which observation most directly demonstrates that gelatin imbibition can generate pressure?
A.
A dry gelatin plug expands and exerts force against the walls of a tightly fitting container
B.
A gelatin solution evaporates more rapidly when exposed to air
C.
A gelatin sample becomes electrically conductive after drying
D.
A gelatin strip loses mass immediately after being immersed in water
Correct Answer:
A dry gelatin plug expands and exerts force against the walls of a tightly fitting container
Explanation:
During imbibition, gelatin takes up water and swells. If its expansion is mechanically restricted, the swelling produces considerable imbibitional pressure against the surrounding container.
3. A gelatin block is divided into two equal pieces. One piece is dry and the other has already absorbed water. Which piece generally has the greater capacity to imbibe additional water?
A.
The dry piece, because its water potential is more negative
B.
The hydrated piece, because water-filled pores attract unlimited water
C.
Both pieces, because imbibition is independent of hydration state
D.
The hydrated piece, because its solute concentration is necessarily higher
Correct Answer:
The dry piece, because its water potential is more negative
Explanation:
Dry gelatin has a stronger deficit of water and therefore a more negative water potential than partially hydrated gelatin. Water is consequently drawn into the dry gelatin more strongly, although the capacity declines as hydration increases.
4. Which change would most directly reduce the rate of water uptake by a dry gelatin sheet without changing its chemical composition?
A.
Reducing the exposed surface area of the sheet
B.
Increasing the number of hydrophilic groups in the gelatin
C.
Increasing the difference in water potential between gelatin and water
D.
Increasing the porosity of the gelatin network
Correct Answer:
Reducing the exposed surface area of the sheet
Explanation:
Water enters gelatin through its exposed hydrophilic surfaces. A smaller exposed surface reduces the area available for adsorption and penetration, thereby lowering the rate of imbibition.
5. Why does a dry gelatin sheet usually swell more readily in pure water than in a concentrated salt solution?
A.
Pure water generally provides a greater water-potential gradient toward the dry gelatin
B.
Salt ions chemically digest gelatin before water enters it
C.
Pure water prevents all molecular movement within gelatin
D.
Concentrated salt solution converts gelatin into a hydrophobic substance
Correct Answer:
Pure water generally provides a greater water-potential gradient toward the dry gelatin
Explanation:
A concentrated solution has a lower water potential than pure water. Therefore, the difference in water potential between the external liquid and dry gelatin is usually smaller in the salt solution, reducing imbibitional water uptake and swelling.
6. Which statement best distinguishes gelatin imbibition from ordinary dissolution of a substance in water?
A.
Gelatin first takes up water and swells as a colloidal network rather than immediately dispersing as individual solute molecules
B.
Gelatin imbibition requires a selectively permeable membrane, whereas dissolution never involves water
C.
Gelatin imbibition occurs only when gelatin molecules are converted into gases
D.
Gelatin dissolves completely without any adsorption of water on its molecular surfaces
Correct Answer:
Gelatin first takes up water and swells as a colloidal network rather than immediately dispersing as individual solute molecules
Explanation:
Imbibition involves adsorption and entry of water into the spaces of a hydrophilic colloidal matrix. Gelatin therefore swells as a network; this is distinct from simple dissolution into independently dispersed molecules.
7. A dry gelatin sample is placed in water at two temperatures, with all other conditions identical. Within a moderate range, the warmer sample is expected to imbibe water faster mainly because warming
A.
increases molecular movement and facilitates penetration of water into the gelatin matrix
B.
eliminates the hydrophilic groups responsible for water adsorption
C.
makes water unable to interact with the gelatin surface
D.
changes imbibition into active transport
Correct Answer:
increases molecular movement and facilitates penetration of water into the gelatin matrix
Explanation:
Moderate warming generally increases molecular motion and diffusion, allowing water to enter the hydrophilic gelatin network more rapidly. The process remains physical imbibition, not active transport.
8. If a gelatin strip is allowed to imbibe water until its dimensions become nearly constant, which conclusion is most appropriate?
A.
The net driving force for further imbibition has greatly decreased
B.
The gelatin has begun pumping water out using metabolic energy
C.
The gelatin has become a selectively permeable living tissue
D.
The absorbed water has been chemically converted into gelatin
Correct Answer:
The net driving force for further imbibition has greatly decreased
Explanation:
As gelatin hydrates, its water deficit and water-potential difference decline. Consequently, the net force drawing additional water into the matrix becomes small, and swelling approaches equilibrium.
9. A dry gelatin plug is tightly enclosed in a rigid vessel containing a small amount of water. After complete hydration, the vessel is found to be under pressure. The pressure arose because
A.
water adsorption caused the gelatin network to expand against mechanical resistance
B.
water was actively secreted by cells inside the gelatin
C.
the gelatin produced gas during respiration
D.
salt crystals formed inside the gelatin and expanded
Correct Answer:
water adsorption caused the gelatin network to expand against mechanical resistance
Explanation:
Gelatin absorbs water through its hydrophilic matrix and increases in volume. When rigid walls prevent free expansion, the resulting swelling is expressed as pressure on the vessel.
10. Which combination would be expected to produce the greatest initial imbibition of water by a gelatin sample?
A.
Finely divided, completely dry gelatin exposed to pure water
B.
A compact, fully hydrated gelatin block exposed to concentrated salt solution
C.
A compact, partially hydrated gelatin block exposed to pure water
D.
Finely divided, completely dry gelatin exposed to a concentrated salt solution
Correct Answer:
Finely divided, completely dry gelatin exposed to pure water
Explanation:
Dry gelatin has a strong water deficit, fine division provides a large exposed surface area, and pure water offers a relatively high water potential. Together these conditions maximize the initial tendency and rate of gelatin imbibition.
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