Question

Identify the incorrect statement among the following:

• A. Viscosity of liquid always decreases with increase in temperature.
• B. Surface tension of liquid always decreases with increase in temperature.
• C. Viscosity of liquid always increases in presence of impurity.
• D. Surface tension of liquid always increases in presence of impurity.

Answer 1

The Correct Option is C

• Option 1: Correct. Viscosity decreases with an increase in temperature because the intermolecular forces are weakened, allowing liquid molecules to flow more easily.
• Option 2: Correct. Surface tension decreases with temperature due to reduced cohesive forces at the liquid surface.
• Option 3: Incorrect. Impurities increase viscosity by disrupting the liquid’s intermolecular interactions, making it harder for molecules to flow.
• Option 4: Correct. The effect of impurities on surface tension depends on the type of impurity. Impurities can either increase or decrease surface tension. For example, surfactants lower surface tension, while some other impurities might increase it.

Therefore, option 3 is incorrect.

Answer 2

Incorrect Statements:

Option 3 and Option 4

Explanation:

• Option 1: Generally true. Increased temperature reduces intermolecular forces, decreasing viscosity.
• Option 2: Generally true. Increased temperature weakens intermolecular forces, decreasing surface tension.
• Option 3: Incorrect. Impurities can either increase or decrease viscosity depending on their nature.
• Option 4: Incorrect. Some impurities, like surfactants, can decrease surface tension.