Given below are two statements, one is labelled as Assertion (A) and the other one labelled as Reason (R).

Assertion (A): Surface tension of water is very high (72.7 dynes/cm) compared to other liquids.

Reason (R): High attraction of water molecules for each other is because of H bond.

In light of the above statements, choose the correct answer from the options given below.

Correct option is A

Explanation of the Correct Option (a): Both (A) and (R) are true and (R) is the correct explanation of (A)
Why Assertion (A) is CORRECT:
· Water has an unusually high surface tension.
· At 20°C, surface tension of water ≈ 72.7 dynes/cm.
· This value is higher than most common liquids.
Why Reason (R) is CORRECT:
· Water molecules exhibit strong intermolecular attraction.
· This attraction arises due to hydrogen bonding (H-bonding) between water molecules.
Why (R) Correctly Explains (A):
· Hydrogen bonds create a cohesive force at the surface of water.
· This strong cohesion leads to high surface tension.
· Hence, the reason directly explains the assertion.
Explanation of Other Options
Option (b):
· Incorrect because:
· Hydrogen bonding is the primary reason for high surface tension.
Option (c):
· Incorrect because:
· Reason (R) is factually correct.
Option (d):
· Incorrect because:
· Assertion (A) is also correct.
Key Points:
· Surface tension of water ≈ 72.7 dynes/cm at 20°C
· Caused by hydrogen bonding
· Responsible for:
· Capillary rise
· Formation of water droplets
· Movement of water in soils and plants