Question

The meniscus formed by mercury in a test tube is-
A. Convex
B. Concave
C. No meniscus is formed
D. None of these

Answer 1

Hint: A meniscus may ascend or descend. It all depends on whether the liquid's molecules are more attracted to the substance outside, or to itself. The justification for this is attributed to cohesion and adhesion.

Complete Step-by-Step solution:
A concave meniscus develops when the liquid molecules are drawn to those in the vessel, which is what you usually would see. It occurs with water and a tube made of glass. A convex meniscus occurs because, as with mercury and glass, the molecules have a greater attraction to each other than to the container. A flat meniscus develops when water is inserted into certain types of plastic tubes; tubes made from various materials that water does not cling to. Anyway, by reading the middle of the liquid in the tube you can get the true volume of the liquid.
Therefore, when water is poured in a glass bottle, surface tension draws the water molecules to the sides of the glass and since adhesion overcomes the binding forces, the water gradually climbs the vessel. This is not happening with Mercury, since the reverse is happening with water. Cohesion forces are greater than their glazing attraction, it's adhesion. It has the opposite effect which means it is convex.
Hence, the meniscus that is formed is convex. Thus, we can say that option A is the correct option.

Note: Cohesion is the tendency of water molecules to stay together due to hydrogen bonds. Adhesion is the tendency of water to bind to certain polar surfaces, regardless of the polarity of water.