Surface tension of a liquid is a molecular phenomenon of liquids involving the force of cohesion along the liquid molecules. It is scalar quantity and is numerically equal to the surface energy. Numerically, it is proved that the potential soluble salts and surface active substance. Sparingly soluble salts and surface active substances decrease the surface tension of the liquid. However, the fairly soluble solutes increase the surface tension of the liquid. Surface tension of a liquid is independent of surface area but it depends on the intermolecular forces and the temperature.
Which of the following has the highest surface tension ?

Options

A. Water
B. Soap in water
C. Detergent in water
D. Glycerol in water.

Explanation

To determine which liquid has the highest surface tension, we need to consider the factors that influence surface tension, particularly the intermolecular forces, especially hydrogen bonding.

### Step-by-Step Solution:

1. **Understand Surface Tension**: Surface tension is a property of liquids that arises from the cohesive forces between liquid molecules. It is a scalar quantity and is influenced by the strength of intermolecular forces.

2. **Identify Key Factors**: The surface tension of a liquid depends primarily on:
- Intermolecular forces (cohesion)
- Temperature
- The presence of solutes (which can either increase or decrease surface tension)

3. **Focus on Hydrogen Bonding**: Among the various intermolecular forces, hydrogen bonding is a significant contributor to high surface tension. Liquids with strong hydrogen bonding will generally exhibit higher surface tension.

4. **Compare the Options**: If we have a list of liquids (e.g., water, glycerol, ethanol, etc.), we need to evaluate their hydrogen bonding capabilities:
- **Water (H₂O)**: Exhibits strong hydrogen bonding due to the presence of two hydrogen atoms bonded to one oxygen atom.
- **Glycerol (C₃H₈O₃)**: Contains three hydroxyl (OH) groups, leading to extensive hydrogen bonding.
- **Ethanol (C₂H₅OH)**: Has one hydroxyl group, resulting in less hydrogen bonding compared to glycerol and water.

5. **Determine the Liquid with Maximum Hydrogen Bonding**: Among the options, glycerol has the highest number of hydroxyl groups, leading to maximum hydrogen bonding. This results in the highest surface tension.

6. **Conclusion**: Based on the analysis, glycerol has the highest surface tension due to its extensive hydrogen bonding capabilities.

### Final Answer:
**Glycerol has the highest surface tension.**