Physical Properties of Solutions

I. Review Matter Mixture Homogeneous Heterogeneous Pure Substance Compound Element Separate Physically Separate Chemically

a. Mixture combination of two or more pure substances in which each pure substance retains its individual chemical identities; can be physically separated (not chemically bonded together)

Types of Mixtures i. Heterogeneous—does not have uniform composition and the individual substances remain distinct; you can see the different components separately; does not have fixed proportions (ex: salad, trail mix, air (atmosphere), sea water) ii. Homogeneous—composition of the mixture is the same throughout; components blend together to look uniform; mixed at the molecular level and has a single phase; different components are not noticeable

1. Homogeneous mixture=solutions -particles of one substance are dissolved and evenly mixed among the particles of another substance; no restriction on the nature of the substances involved Dissolving—one substance disperses throughout another Crystallization—process in which the dissolved solute comes out of solution and forms crystals *Note: Both precipitation and crystallization describe the separation of excess solid substance from a supersaturated solution; however solids formed by the two process differ in appearance

Types of Solutions

Solution Solvent Solute Soft drink (l) H2O Sugar, CO2 Air (g) N2 O2, Ar, CH4 Steel (s) Fe C

II. Physical Properties of Solutions a. Solute—substance that gets dissolved or dispersed in a solution; present in a smaller amount; dispersed throughout the solvent, occupy positions that are normally taken by solvent molecules b. Solvent—the substance that does the dissolving; present in a larger amount; phase is retained in solution c. Solubility— how much solute will dissolve in a solvent at a specific temp; soln are characterized by their capacity to do so

aqueous solutions of KMnO4 Solubility Soluble Insoluble aqueous solutions of KMnO4 CdS PbS Ni(OH)2 Al(OH)3

c. Solubility Soluble—the solutes ability to dissolve in a solvent a. Miscible—two liquids are completely soluble in each other in all proportions 2. Insoluble—the solute is not able to dissolve in the b. Immiscible—two liquids that can be mixed together but separate shortly after you stop mixing them

Are the solutions the same? How can we describe them?

ii. Concentration Concentrated Dilute Add solvent

ii. Concentration —amount of solute present for a given amount of solution; relative or absolute 1. Concentrated—contains greater amount of solute per volume of solution 2. Dilute—contains relatively small amounts of the solute per volume of solution **relative amounts

Saturation Unsaturated Saturated Supersaturated

iii. Saturation -solutions are also characterized by their capacity to dissolve a solute 1. Saturated—contains the maximum amount of a solute that will dissolve in a given solvent at a specific temperature 2. Unsaturated—contains less solute than it has the capacity to dissolve 3. Supersaturated—contains more solute than is present in a saturated soln; not very stable (in time some of the solute will come out of the supersaturated soln as crystals) ** absolute amounts

d. Solvation —process in which an ion or molecule is surrounded by solvent molecules arranged in a specific manner

Three types of interactions in the solution process: solvent-solvent interaction solute-solute interaction solvent-solute interaction Molecular view of the formation of solution

i. Rules for solvation: “like dissolves like” Two substances with similar intermolecular forces are likely to be soluble in each other. non-polar molecules are soluble in non-polar solvents CCl4 in C6H6 polar molecules are soluble in polar solvents C2H5OH in H2O ionic compounds are more soluble in polar solvents NaCl in H2O or NH3 (l)

glucose in water

ii. Factors that Affect Rate of Solvation driving force: increase collisions between solute and solvent particles Agitation (stirring) Increase surface area (smaller solute particles) Increase Temperature Increase Pressure *our focus = solutions involving at least one liquid component; liquid solvent is most likely water

III. Aqueous Solutions -Solution where the solvent is specifically water

a. Hydration process in which an ion is surrounded by water molecules arranged in a specific manner. d+ d- H2O Hydrolysis is the opposite of acid/base Strong Electrolyte – 100% dissociation NaCl (s) Na+ (aq) + Cl- (aq) H2O

b. Electrolytes i. An electrolyte is a substance that, when dissolved in water, results in a solution that can conduct electricity. ii. A weak electrolyte is a substance that, when dissolved, results in a solution that conducts a weak current because only part of the solute exists as ions. iii. A nonelectrolyte is a substance that, when dissolved, results in a solution that does not conduct electricity.

Strong acids Strong bases HI HBr HClO4 HCl H2SO4 HNO3 NaOH KOH LiOH RbOH CsOH        Ca(OH)2 Ba(OH)2 Sr(OH)2 Strong acids/bases are strong electrolytes and will completely dissociate in water.

Weak Electrolyte – not completely dissociated HCl(l) H+(aq) + Cl−(aq) CH3COOH(aq) H+(aq) + CH3COO−(aq) Weak Electrolyte – not completely dissociated

Review of Concepts The diagrams here show three compounds AB2 (a), AC2 (b), and AD2 (c) dissolved in water. Which is the strongest electrolyte and which is the weakest? (For simplicity, water molecules are not shown.)