Question

q20. when adhesive force is greater than cohesive force in liquid of a glass tube is
a. convex meniscus
b. concave meniscus
c. surface tensions
d. capillary actions
q21. if adhesive force is greater than cohesive force in liquid of a glass tube, the contact angle between liquid and glass is
a. less than 90 degrees
b. greater than 90 degrees
c. equal to 90 degrees
d. none of above

Explanation:

When adhesive force is greater than cohesive force in a liquid - glass system, the liquid wets the glass. This results in a concave meniscus as the liquid is attracted more to the glass surface than to itself. Also, the contact angle between the liquid and glass is less than 90 degrees when the liquid wets the solid surface.

Answer:

Q20. B. concave meniscus
Q21. A. less than 90 degrees