(A) : Surface tension decreases with increase of temperature.
(R) : With increase of temperature kinetic energy of molecules increases and there is decrease in intermolecular forces of attraction.

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(A) is true but (R) is false

Both (A) and (R) are correct and (R) is the correct explanation of (A)

Both (A) and (R) are false

Both (A) and (R) are correct but (R) is not the correct explanation of (A)

answer is A.

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Detailed Solution

Surface tension is the cohesive force per unit length between the molecules at the surface of a liquid.
The cohesive forces are the result of the attractive forces between the molecules in the bulk of the liquid.
When the temperature of the liquid increases, the kinetic energy of the molecules also increases.
The increased kinetic energy causes the molecules to move more rapidly and increases the average distance between the molecules.
This results in a decrease in the intermolecular forces of attraction between the molecules, which leads to a decrease in the surface tension of the liquid.
Therefore, statement (R) correctly explains why the surface tension of a liquid decreases with an increase in temperature.

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