CHEM 1120 1st Edition Lecture 4Outline of Last Lecture I. Continuing with Colligative Properties, Boiling Point ElevationII. Freezing Point DepressionIII.OsmosisOutline of Current Lecture I. Colligative Properties of Electrolyte SolutionsA. van’t Hoff Factor II. ColloidsA. Definitions and typesB. Hydrophillic vs Hydrophobic ColloidsCurrent LectureI. Electrolytes often do not dissociate all the way in solutions. This is where the van’t Hoff Factor works its way into chemistry. The van’t Hoff Factor (i)is equal to the moles of particles in a solution over the moles of solute dissolved in a solution. For salts, it is pretty simple. You just take the number of ions over the formula units. This seems complicated, but let me show you an example. For NaCl, it dissolves into two ions and the formula units is equal to one, so two divided by one is two. This is the same process for most dissociating salts. However many ions it dissolves into is equal to the expected van’t Hoff Factor for that solution. Another example is K2SO4. Potassium sulfate dissociates into three ions, therefore making the van’t Hoff Factor for that solution equal to three. Although salts dissociate and there van’t Hoff Factor is the number of ions, this is not true for molecules that do not dissociate. For these other molecules, including sucrose and others similar, the van’t Hoff Factor is usually just one. These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.**The actual van’t Hoff Factors are slightly different than the expected values because of something called ion pair formation. II. A. As we remember from earlier lectures, a solution is a homogeneous mixture of two or more substances (Example: Na+ and Cl-, 0.1-1 particle diameter). We need to remember this definition to compare solutions to suspensions and colloids. Suspension = a heterogeneous mixture with dispersed particles large enough to be seen Example: corn starch (1000+ nm particlediameter)Colloid =a mixture with dispersed particles larger than a solution’s, butsmaller than a suspension’s Example: fog/clouds (1-1000 nm particle diameter)Colloids may not always be liquids and are found everywhere. Additionally when talking about colloids, the Tyndall Effect comes up as well. The Tyndall Effect is a phenomenon that states that colloidal suspensions canscatter rays of light.SOLUTION COLLOID SUSPENSIONPARTICLE SIZE 0.1-1 nm 1-1000nm 1000+ nmPARTICLE TYPE ions and small moleculesparticles and large moleculeslarge particlesPARTICLES do not settle do not settle settleFILTERABLE no no yesUNIFORMITY homogeneous intermediate heterogeneousTYNDALL EFFECT no yes yesLIGHT does not scatter scatters scattersB. Hydrophilic and Hydrophobic Colloids:Hydrophilic = “water loving” Hydrophobic = “water fearing” Remember, like dissolves like, so polar molecules will dissolve in water because water is polar, and octane, a nonpolar molecule, will be insoluble in polar water. Hydrophilic Colloids: •Dispersed particles are large molecules •the core may be hydrophobic•the surface is hydrophilic•surface groups hydrogen bond to waterHydrophobic Colloids:must be stabilized by —> ions absorbed on the particle’s surface, or by hydrophilic groups on the particle’s surface •one nonpolar particle has a greater attraction for another nonpolar particle than it does for water•absorbed ions interact with water and particles repel each other•the tail of a hydrophobic colloid is nonpolar/hydrophobic and the head is polar/hydrophilicColloids can help to emulsify fats and oils in aqueous solutions. An emulsifier causes something that normally does not dissolve in a solvent to do so.The motion of colloids is mainly due to the numerous amount of collisions with the much waller solvent particles/molecules. (Brownian