chemistry : class11 Capillary Depression : Surface tension : States of Matter: Gases and Liquids MCQ Questions and Answers
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Capillary Depression
MCQ questions and answers.
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MCQ Questions
1. Capillary depression occurs when a liquid level in a narrow tube becomes:
A.
Higher than the liquid level outside the tube
B.
Lower than the liquid level outside the tube
C.
Equal to the liquid level outside the tube
D.
Unchanged in all cases
Correct Answer:
Lower than the liquid level outside the tube
Explanation:
Capillary depression is the lowering of a liquid surface in a narrow capillary tube compared with the liquid surface outside the tube.
2. Which liquid commonly shows capillary depression in a glass capillary tube?
A.
Water
B.
Mercury
C.
Alcohol
D.
Kerosene
Correct Answer:
Mercury
Explanation:
Mercury does not wet glass and its level is depressed in a glass capillary tube.
3. The meniscus of mercury in a glass capillary tube is:
A.
Concave
B.
Convex
C.
Plane
D.
Irregular in every case
Correct Answer:
Convex
Explanation:
Mercury forms a convex meniscus in glass because the cohesive forces between mercury particles are greater than the adhesive forces between mercury and glass.
4. Capillary depression is observed when the angle of contact between the liquid and the tube is:
A.
Less than 90 degrees
B.
Equal to 0 degrees
C.
Greater than 90 degrees
D.
Always equal to 45 degrees
Correct Answer:
Greater than 90 degrees
Explanation:
A contact angle greater than 90 degrees indicates that the liquid does not wet the tube, leading to capillary depression.
5. In a narrow glass tube, mercury shows capillary depression mainly because:
A.
Mercury strongly wets glass
B.
Adhesion between mercury and glass is weaker than cohesion within mercury
C.
Mercury has no surface tension
D.
Glass pushes mercury upward
Correct Answer:
Adhesion between mercury and glass is weaker than cohesion within mercury
Explanation:
The stronger cohesive forces within mercury compared with its adhesive forces toward glass produce a convex meniscus and capillary depression.
6. If the radius of a capillary tube is decreased, the capillary depression of mercury generally:
A.
Increases
B.
Decreases to zero
C.
Remains unchanged
D.
Changes into capillary rise
Correct Answer:
Increases
Explanation:
The magnitude of capillary depression is inversely related to the radius of the capillary tube, so a narrower tube produces greater depression.
7. The liquid surface inside a capillary tube is lower than the outside surface in capillary depression because the liquid:
A.
Does not wet the walls of the tube
B.
Has no intermolecular attraction
C.
Always evaporates inside the tube
D.
Has zero density
Correct Answer:
Does not wet the walls of the tube
Explanation:
A non-wetting liquid has a contact angle greater than 90 degrees and forms a convex meniscus with a lower level inside the tube.
8. For capillary depression, the surface of the liquid near the tube wall is:
A.
Higher than the center
B.
Lower than the center
C.
At the same height as the center
D.
Always flat
Correct Answer:
Higher than the center
Explanation:
A convex meniscus is formed in capillary depression, so the liquid surface is higher near the walls and lower at the center.
9. Which combination is associated with capillary depression?
A.
Water in glass and concave meniscus
B.
Mercury in glass and convex meniscus
C.
Water in glass and convex meniscus
D.
Mercury in glass and concave meniscus
Correct Answer:
Mercury in glass and convex meniscus
Explanation:
Mercury in a glass capillary does not wet the glass, forms a convex meniscus, and undergoes capillary depression.
10. The capillary depression of a liquid is measured as the vertical distance between:
A.
The top of the tube and the liquid surface
B.
The liquid surface inside the tube and the liquid surface outside the tube
C.
The bottom of the tube and the liquid surface
D.
The tube wall and the center of the tube
Correct Answer:
The liquid surface inside the tube and the liquid surface outside the tube
Explanation:
Capillary depression is the vertical lowering of the liquid level inside the capillary relative to the level of the liquid outside.
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