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Which of the following statements is true ?
A.All liquids have concave meniscus
B.All liquids have convex meniscus
C.Mercury has convex and other liquids have concave meniscus
D.Mercury has concave and other liquids have convex meniscus

seo-qna
Last updated date: 13th Jun 2024
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Answer
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Hint: Convex meniscus is formed when the cohesive forces are stronger , that is , attractive forces between molecules of same substance whereas concave meniscus is formed when the adhesive forces are stronger , that is , attraction between molecules of different substance.

Complete step by step answer:
When we put one end of a capillary tube into a liquid , it is found that the liquid rises into the capillary tube upto a certain height. This rise is due to the inward pull of surface tension acting on the surface which pushes the liquid into the capillary tube . A curved surface is formed in the capillary tube known as the meniscus .
There are two kinds of attractive forces acting between the molecules: they are cohesive and adhesive forces. Let us consider two liquids: water and mercury.
In case of taken in a glass tube the adhesive forces are stronger (force of attraction between water molecules and glass molecules ) than the cohesive forces ,hence concave meniscus is formed. Whereas in case of mercury the cohesive forces are stronger ( force of attraction between mercury molecules is stronger ) hence , convex meniscus is formed

So, the correct answer is Option C.

Note:
Mercury is an exception where the cohesive forces are stronger but generally in case of all other liquids adhesive forces are stronger so generally we see concave meniscus in all liquids .Meniscus has the tendency to go up and down which is depend on the molecules of liquid