A capillary tube is inserted in mercury kept in an open container.Asse...
Assertion: The mercury level inside the tube shall rise above the level of mercury outside.
Reason: The cohesive force between the molecules of mercury is greater than the adhesive force between mercury and glass.
To understand why option D is the correct answer, let's analyze the given situation and evaluate the assertion and reason individually.
Assertion (A): The mercury level inside the tube shall rise above the level of mercury outside.
When a capillary tube is inserted in mercury kept in an open container, the mercury level inside the tube rises above the level of mercury outside. This phenomenon is known as capillary action. Capillary action is the ability of a liquid to flow in narrow spaces against the force of gravity. It occurs due to the combined effects of cohesive forces between liquid molecules and adhesive forces between the liquid and the material of the tube (in this case, glass).
Reason (R): The cohesive force between the molecules of mercury is greater than the adhesive force between mercury and glass.
The reason given states that the cohesive force between the molecules of mercury is greater than the adhesive force between mercury and glass. Cohesion refers to the intermolecular attraction between like molecules (in this case, mercury molecules). Adhesion, on the other hand, refers to the attraction between unlike molecules (mercury and glass).
In the case of mercury, the cohesive forces between its molecules are relatively strong, leading to a concave meniscus when it comes into contact with a glass surface. In other words, the mercury molecules tend to attract each other more strongly than they adhere to the glass. As a result, the mercury inside the capillary tube rises above the level of mercury outside.
Explanation:
The given assertion and reason are both true, but the reason does not correctly explain why the mercury level inside the tube rises above the level outside. The reason suggests that the cohesive force between mercury molecules being greater than the adhesive force between mercury and glass is the cause of the capillary action. However, the actual cause of capillary action is the adhesive force between the liquid and the tube material being greater than the cohesive force between the liquid molecules.
In capillary action, the adhesive force between the liquid (mercury) and the capillary tube (glass) is stronger than the cohesive force between the liquid molecules. This imbalance of forces causes the liquid to be drawn up into the tube, resulting in a higher level inside compared to outside.
Therefore, the correct answer is option D: A is false, but R is true.
A capillary tube is inserted in mercury kept in an open container.Asse...
Because as when adhesion is greater than cohesion in a liquid,then the molecules will stick to the glass surface and make it wet.So in this way the liquid level rises up in glass tube.This happens when liquid is water.but when liquid is mercury, then cohesion predominates and thus, level of mercury goes down.
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