(solids) Solutions and Other Mixtures

What is a solution? A solution exists when one substance is ‘dissolved’ in another. This is considered a ‘physical process’. Solute=the substance that gets dissolved. Solvent=the substance that does the dissolving. Solution=Solute + Solvent.

Molarity A unit of concentration Units are mole of solute/liter solution Conversion factor! 

Molarity One measure of solution concentration is Molarity. Molarity = moles of solute/Liters of solution. Example: What is the molarity of a solution in which 116.86g of NaCl is dissolved in enough water to come to the 5.0 L line?

Phase Change

Phase Change

Phase Diagram Water Everything else

Solutions vs. Colloids and Suspensions Type of Mixture Particle Size Solution (homogeneous) 0.1-1 nm(No Tyndall) Colloid (heterogeneous) 1-1000nm(Tyndall) Suspension 1000nm and greater (Tyndall)

Electrolytes vs. Non-electrolytes Electrolyte-a compound that conducts electricity when in a molten state or in aqueous solution Ionic compounds Non-electrolyte-a compound that does not conduct electricity. Covalent compounds

Types of Solutions (based upon solutes and solvents) Gas in Gas (Air) Gas in Liquid (seltzer or soda) Liquid in Liquid (Vinegar) Solid in Liquid (Salt water solution) Solid in Solid-Brass

What does it mean to dissolve? Dissociation (Ionic Solvation)-when an ionic solute, or salt, dissolves in a solvent, the solvent “rips” the individual ions away from the crystal.

What does it mean to dissolve? Molecular Solvation-when a molecular solute, such as sugar, dissolves, the solvent separates the sugar molecules from their neighbors But does not rip the sugar molecules into individual C, H, and O atoms.

Factors affecting the rate of solubility (not degree of solubility) Solids dissolved in liquids-increased rate of solvation increasing temperature increasing surface area (by creating smaller particles) agitation

How much solute dissolves? Solubility= grams solute/100 g water Types of solutions based upon their degree of solvation: 1. unsaturated-the solvent holds less solute than is theoretically possible. 2. saturated-the solvent holds the maximum amount of solute that is theoretically possible

Factors affecting degree of solubility Supersaturated-solvent holds more solute than is theoretically possible. Factors affecting degree of solubility Solids in Liquids-as T increases, solubility increases. Gases in Liquids-as T increases, solubility decreases. As P increases solubility increases.

“Like Dissolves Like” “Like dissolves like,” but why? Polar molecules have positive and negative regions. Solute and solvent are both polar - The opposite charges help attract the particles to each other and solvation occurs. One polar, one nonpolar - There is no attraction between the particles and solvation does not occur. These substances are described as insoluble or immiscible. A polar water molecule. Both substances are polar. Opposite charges attract One polar, one nonpolar. No attraction

“Like Dissolves Like” Everyday Example Water and grease are insoluble because water is polar and grease is nonpolar. Soap helps dissolve greasy stains because it contains a polar head and a long, nonpolar tail. The nonpolar tail mixes with the grease while the polar head mixes with the water…goodbye greasy stain!

Colligative Properties Definition: Properties that are affected only by the number of particles that dissolve in the solvent. Examples: 1. Freezing Point Depression (ie salt on the roads) 2. Boiling Point Elevation