Final answer:
With equal forces of cohesion and adhesion, a liquid exhibits neither capillary rise nor fall in a capillary tube, resulting in a flat meniscus.
Step-by-step explanation:
When a liquid has equal forces of cohesion and adhesion, the behavior of the liquid in a capillary tube is determined by the balance of these forces. As for water, strong adhesion to the glass causes a capillary rise, while for mercury, stronger cohesion than adhesion leads to a capillary depression.
If cohesion and adhesion forces are perfectly balanced, there would be no capillary rise or fall, and the liquid level inside the capillary tube should stay at the same level as the surrounding liquid. Instead of shaping into a concave or convex meniscus, the meniscus should be flat. This scenario, however, is rare due to the complex intermolecular forces involved.