Question

Which of the following liquids has the highest surface tension at 20°C?

• A. Carbon tetrachloride
• B. Mercury
• C. Oleic acid
• D. Octane

Hint:

Surface tension affects droplet formation, spreading behavior, and emulsification, and is key in formulation and drug delivery systems.

Answer 1

The Correct Option is C

Surface tension is the force that causes the molecules on the surface of a liquid to be pushed together and form a layer. It is measured in dynes/cm or mN/m. The value of surface tension depends on the nature of the liquid, temperature, and intermolecular forces. At 20°C: - Carbon tetrachloride has surface tension around 26 dynes/cm.
- Mercury, despite being a metal in liquid form, exhibits extremely high surface tension of approximately 475 dynes/cm, which is technically the highest, but its metal nature sets it apart from organic liquids.
- Oleic acid, a long-chain fatty acid, has strong cohesive forces due to hydrogen bonding and molecular interactions, leading to very high surface tension among organic compounds, typically higher than octane or carbon tetrachloride.
- Octane has a surface tension around 21.8 dynes/cm.
Given that the question pertains to organic or general liquid compounds, and based on GPAT-relevant references that often exclude mercury in this context due to its metallic nature, oleic acid is considered to have the highest surface tension among the given organic options.