Surface Tension :Pp-II ( Practical)

The correct answer is "Kraft point". The Kraft point is the temperature at which the solubility of a surfactant is equal to its Critical Micelle Concentration (CMC). At this temperature, the surfactant molecules form micelles in the solution, which is a characteristic behavior of surfactants at their CMC. The boiling point and melting point are unrelated to the solubility of surfactants, so they are not the correct answers.

Griffin is the correct answer because he is the scientist who discovered the equation for HLB (Hydrophilic-Lipophilic Balance) value. The HLB system is used to determine the emulsifying properties of surfactants, which is essential in various industries such as cosmetics, pharmaceuticals, and food. Griffin's contribution in developing this equation has greatly influenced the understanding and application of surfactants in these industries.

The bubble point test is specifically performed to determine the surface tension of a liquid in a capillary tube. This test involves gradually increasing the pressure on the liquid until a bubble is formed at the end of the capillary tube. The pressure at which the bubble forms is directly related to the surface tension of the liquid. Therefore, the correct answer is surface tension of liquid in a capillary tube.

Isoelectric pH refers to the pH at which the net charge of a surfactant molecule is zero. At this pH, the number of positive and negative charges on the surfactant molecule is balanced, resulting in no overall charge. This is an important property as it affects the behavior and solubility of the surfactant in different environments. Critical pH, on the other hand, refers to the pH at which a specific property or behavior of a substance changes significantly. Electric pH is not a recognized term in the context of surfactants.

Surface tension is a property of liquids that is caused by the cohesive forces between the molecules at the surface. When the temperature of a liquid increases, the kinetic energy of the molecules also increases. This increased kinetic energy disrupts the cohesive forces between the molecules, causing the surface tension to decrease. Therefore, as the temperature increases, the surface tension decreases.

The correct answer is "Less." When the value of Wa (the adhesive force between the oil and water molecules) is less than Wc (the cohesive force between the water molecules), the oil will spread on the water surface. This is because the adhesive force between the oil and water is weaker than the cohesive force within the water, allowing the oil molecules to spread out and cover a larger area on the water.

The aggregation number refers to the number of surfactant molecules present in micelles. It represents the minimum number of surfactant molecules required for micelle formation. Micelles are formed when surfactant molecules arrange themselves in a specific structure in a solvent, usually in the form of a spherical or cylindrical shape. The aggregation number is important in determining the stability and properties of micelles.

The surface tension of a liquid determines the shape and size of its droplets. A higher surface tension means that the liquid molecules are more strongly attracted to each other, resulting in smaller droplets. Since the surface tension of water is larger than acetone, the drop size of water will be larger than acetone.

In the presence of NaCl, the critical micelle concentration (CMC) of a surfactant decreases. This is because NaCl ions can shield the electrostatic repulsion between surfactant molecules, allowing them to come closer together and form micelles more easily. This effectively lowers the concentration required for micelle formation, resulting in a decrease in the CMC.

Surfactants with high HLB (hydrophilic-lipophilic balance) values have a greater affinity for water and are therefore more hydrophilic. This means that they have a stronger tendency to dissolve and interact with water molecules. Conversely, surfactants with low HLB values are more lipophilic, meaning they have a greater affinity for oils and fats. In summary, a higher HLB value indicates a surfactant is more hydrophilic and less lipophilic, making it more soluble in water.