Surfactant Activity & Application

<blockquote> <p>13 (D)</p> </blockquote> Signup and view all the answers

<p>It indicates the point where surfactant molecules begin to aggregate into micelles. (B)</p> Signup and view all the answers

<p>A pronounced fall in surface tension is observed, followed by a slight decrease after cmc. (A)</p> Signup and view all the answers

<p>The surface excess concentration of surfactants at the air-liquid interface. (D)</p> Signup and view all the answers

<p>Monomers exist only below the cmc, while micelles exist only above it. (A)</p> Signup and view all the answers

<p>1/pNA m2 multiplied by 10^18 to convert to nm2. (C)</p> Signup and view all the answers

<p>They aggregate into micelles. (B)</p> Signup and view all the answers

<p>When the continuous phase is saturated. (A)</p> Signup and view all the answers

<p>It maintains a continuous phase for micelles to exist. (A)</p> Signup and view all the answers

<p>It has no effect on surface tension. (C)</p> Signup and view all the answers

<p>Presence of poorly soluble substances. (C)</p> Signup and view all the answers

<p>They coalesce into larger droplets. (A)</p> Signup and view all the answers

<p>They stabilize poorly soluble substances in solution. (D)</p> Signup and view all the answers

<p>Micelles attract water molecules to form stable structures. (A)</p> Signup and view all the answers

<p>cmc increases with increasing chain length. (D)</p> Signup and view all the answers

<p>The size of micelles decreases due to reduced charge repulsion. (C)</p> Signup and view all the answers

<p>Their solubility decreases with temperature, becoming cloudy. (A)</p> Signup and view all the answers

<p>Using a more weakly hydrated counter ion. (C)</p> Signup and view all the answers

<p>At the Krafft point. (A)</p> Signup and view all the answers

<p>The aggregation number decreases with chain length. (D)</p> Signup and view all the answers

<p>Two linear phases are observed, with the second phase being less steep. (C)</p> Signup and view all the answers

<p>Oil droplets are encapsulated in the center of micelles. (D)</p> Signup and view all the answers

<p>Increase in the hydrophilic portion of the molecule (C)</p> Signup and view all the answers

<p>Ionic surfactants have repulsive charged head groups (D)</p> Signup and view all the answers

<p>Molecules break and reform continually (B)</p> Signup and view all the answers

<p>Non-ionic micelles are typically ellipsoidal (B)</p> Signup and view all the answers

<p>It decreases cmc and increases micellar size (B)</p> Signup and view all the answers

<p>They are typically spherical with 70-80% of counter ions bound (B)</p> Signup and view all the answers

<p>It influences micelle size and cmc (D)</p> Signup and view all the answers

<p>They possess a higher aggregation number with similar hydrocarbon chains (D)</p> Signup and view all the answers

<p>Conductivity reduces due to the binding of counter ions. (D)</p> Signup and view all the answers

<p>It slows down the movement of ions, limiting their free flow. (A)</p> Signup and view all the answers

<p>They exert a breaking effect counteracting fluid flow and decrease conductance. (B)</p> Signup and view all the answers

<p>A micelle is a larger entity that encounters less resistance. (A)</p> Signup and view all the answers

<p>It decreases conductivity by imposing attractive forces and slowing fluid flow. (C)</p> Signup and view all the answers

<p>An increase in micelles always results in decreased conductivity. (D)</p> Signup and view all the answers

<p>The attractive forces from unbound counter ions. (B)</p> Signup and view all the answers

<p>It reduces the total charge on the micelles due to bound counter ions. (C)</p> Signup and view all the answers

A value that indicates the balance between the hydrophilic (water-loving) and lipophilic (oil-loving) parts of a surfactant molecule.

The process of dissolving a substance (solute) into a solvent, often using surfactants to enhance solubility.

A type of emulsion where the oil droplets are dispersed in a continuous water phase.

The amount of HLB required by a particular oil phase to form a stable emulsion. It's specific to each type of oil.

Mixing different surfactants with varying HLB values to achieve a specific HLB value as needed for a particular formulation.

The minimum concentration of a surfactant at which micelles begin to form in solution.

Aggregates of surfactant molecules in solution, formed above the CMC, consisting of a hydrophobic core and hydrophilic exterior.

The relationship between surface tension (γ) and bulk concentration (Cb) of a surfactant solution, often displayed as a graph.

The process of surfactants accumulating at the interface between two immiscible phases, such as air-water or oil-water.

The process of small droplets coalescing into larger ones, often due to the concentration of surfactant molecules at the surface.

A type of emulsion where tiny droplets of water are dispersed throughout a continuous oil phase. Think mayonnaise.

A molecule that contains both hydrophilic (water-loving) and lipophilic (oil-loving) parts.

An emulsion where the droplets are evenly distributed, forming a smooth and stable product.

Surfactant molecules self-assemble into spherical structures called micelles when their concentration surpasses a critical threshold, known as the critical micelle concentration (CMC). This occurs due to the minimization of free energy within the system.

The tendency of water molecules to surround hydrophobic groups, like the tails of surfactant molecules, results in an unfavorable energy state, as water molecules become more ordered, leading to a decrease in entropy.

The formation of micelles is a dynamic process, constantly breaking and reforming, with an equilibrium established between monomers (individual surfactant molecules) and micelles.

Non-ionic surfactants tend to form micelles at significantly lower concentrations compared to ionic surfactants, due to the absence of repulsive forces between charged head groups.

Ionic micelles are typically spherical and contain a large number of counter ions (oppositely charged ions) bound to the micelle surface.

Non-ionic micelles are generally larger in size than ionic micelles and are often asymmetrically shaped, like ellipsoids. This is due to the entrapment of water molecules within the oxyethylene chains of non-ionic surfactants.

The CMC (critical micelle concentration) is the concentration at which micelle formation begins. The aggregation number is the number of surfactant molecules in each micelle. These parameters can be influenced by several factors including the structure of the hydrophobic and hydrophilic portions of the surfactant molecule.

Non-ionic surfactants generally have a lower CMC (critical micelle concentration) and a higher aggregation number (number of molecules per micelle) compared to ionic surfactants with similar hydrocarbon chains.

The number of surfactant molecules that come together to form a single micelle. It indicates the size and stability of micelles.

The effect of increasing the length of the polyoxyethylene chain in non-ionic surfactants. This results in greater hydrophilicity, leading to a higher CMC.

The influence of the counterion on micelle formation. A less hydrated counterion (larger mass) can interact with the micelle surface, reducing the repulsive forces between head groups, leading to smaller micelle size and a lower CMC.

The effect of adding electrolytes to ionic micelles. Electrolytes decrease repulsive forces between surfactant head groups, resulting in smaller micelle size and a lower CMC.

The temperature at which aqueous solutions of non-ionic surfactants become cloudy due to a decrease in solubility. This is a reversible phenomenon.

The temperature above which the solubility of ionic surfactants increases significantly. This is a critical factor for the use of ionic surfactants in various applications.

The process by which surfactants solubilize substances, including those that are not normally soluble in water, by incorporating them into the micelles. This allows for the formation of stable dispersions.

As you add more surfactant to a solution, the number of micelles increases. This happens because the surfactant molecules start forming these structures to minimize their contact with water.

The ability of a substance to conduct electricity. In the case of ionic micelles, their electrical conductivity is influenced by the movement of ions within the micelle.

The movement of ions within a solution is hindered by the viscosity of the solvent. Micelles can actually reduce the viscosity, because one micelle experiences less drag than 100 individual molecules.

The counter-ions surrounding a micelle exert attractive forces and hold water molecules, creating an 'atmosphere' around it. This creates a fluid flow that opposes the movement of the actual micelle, leading to a decrease in conductance.

Most counter-ions stick to the micelle (bound), reducing its overall charge. These bound counter-ions move in the opposite direction of the micelle, creating a retarding force and further decreasing conductance.

Higher concentrations of electrolytes (salts) in a solution can 'pull' some counter-ions away from the micelle. This can impact the balance of forces and ultimately affect both the size and stability of the micelles.