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ASSESSMENT QUESTIONS:
WEILE WANG
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for class G1 Honors
Chemistry
Questions & Answers
1. Which pair of water molecules shown below are most likely to form a hydrogen bond in
their current positions?
A. Pair I
B. Pair II
C. Pair III
D. All are equally likely to bond in their current positions.
Correct Answer: B. Pair II
Explanation: In order to form a hydrogen bond, the partial negative side (shown in
red) of one water molecule must align with the partial positive side (shown in blue) of
another. Since opposite charges attract, this arrangement best allows the molecules
to form a hydrogen bond.
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2. What is the best explanation for the difference in shape between the two drops shown
below?
A. Hexane is nonpolar and has greater cohesion than glycerin.
B. Glycerin is nonpolar and has greater cohesion than hexane.
C. Hexane is polar and has greater cohesion than glycerin.
D. Glycerin is polar and has greater cohesion than hexane.
Correct Answer: D. Glycerin is polar and has greater cohesion than hexane.
Explanation: Since glycerin is polar, it has strong cohesive forces acting between its
molecules. In this case, cohesive forces are much stronger than adhesive forces
between the liquid and surface. Since strong cohesive forces prevent the liquid from
spreading out, it assumes a rounded shape.
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3. Which of the following provides the best explanation for why the water drop does not
slide off the inclined plane?
A. The polar water molecules are absorbed by the underlying surface.
B. The polar water molecules cause the surface to become temporarily charged,
causing adhesion.
C. The polar water molecules exert strong cohesive forces on one another.
D. The polar water molecules are repelled by the nonpolar surface.
Correct Answer: B. The polar water molecules cause the surface to become
temporarily charged, causing adhesion.
Explanation: Adhesion is responsible for the water drop sticking to the inclined plane
and not sliding off. Adhesion occurs when the charged parts of the water molecules
repel like charges and attract unlike charges in the underlying surface, causing the
surface to become temporarily polar and thus attracted to the water.
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4. As shown below, a ring can be lifted through a fluid without breaking the surface film due
to surface tension. In which type of liquid would you expect to find the greatest surface
tension, and why?
A. Polar liquids, because they have strong cohesive forces.
B. Nonpolar liquids, because they have weak cohesive forces.
C. Polar liquids, because they have weak cohesive forces.
D. Nonpolar liquids, because they have strong cohesive forces.
Correct Answer: A. Polar liquids, because they have strong cohesive forces.
Explanation: Polar liquids experience the greatest surface tension because their
molecules experience stronger cohesive forces than do the molecules of nonpolar
liquids. Since the oppositely charged regions of its molecules are strongly attracted
to one another, the surface of a polar liquid can be “stretched” farther without
breaking. In the above apparatus, the strength of these cohesive forces can be used
to quantitatively determine surface tension, since it is more difficult to remove the
ring if cohesion, and thus surface tension, is stronger.
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5. Why is capillary rise less with hexane than with water, as shown below?
A. Hexane is less polar.
B. Hexane has less cohesion between its molecules.
C. Hexane creates weaker adhesive forces.
D. All of the above.
Correct Answer: D. All of the above.
Explanation: Hexane is less polar than water, leading to weaker adhesive and
cohesive forces, and therefore less capillary rise. Capillary rise is greater in polar
liquids with strong intermolecular forces, which create strong adhesion with the walls
of the tube and strong cohesion between the fluid molecules.
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