Solutions

Solution – homogeneous mixture in which solute & solvent particles are evenly distributed in one another solvent – the dissolving medium; thing that does the dissolving solute –the dissolved particles; thing that is dissolved solutes and solvents can be solids, liquids, or gases

Solubility – amount of solute that dissolves in a quantity of solvent at certain temperature and pressure Solutions can be: a) unsaturated – contains less solute than solvent can possibly dissolve b) saturated – contains as much solute as can be dissolved by solvent

c) supersaturated – contains more solute than can normally be dissolved by solvent; not very stable – slight disturbance to solution will cause solute to precipitate or crystallize

Terms related to solubility soluble – substance that will dissolve in a solvent insoluble – substance that will not dissolve in a solvent miscible – when 2 liquids will dissolve in each other in any proportion (ex: water and ethanol) immiscible – when 2 liquids are insoluble (ex: water and oil)

Electrolytes excellent conductors in liquid state or dissolved in water (aqueous) In order for a solution to carry an electrical current, it must contain ions that are free to move. Acids, bases and ionic compounds all ionize (break into ions) in water to form free ions. http://www.schooltube.com/video/36d820507a4c220061eb/The-Basics-on-Electrolytes

Factors Affecting Solubility agitation of the system – increases collisions between solute and solvent particles particle size – smaller dissolves faster because more surface area temperature – solutes generally dissolve faster at higher temps. – higher kinetic energy at higher temps. – stronger and more frequent collisions between solute and solvent particles - Exception: solubility of gases inversely proportional to temperature

Concentration of Solutions Molarity – M – mols of solute per L of solution Example: 5 M – dissolve 5 mol of solute in enough solvent to make 1 L of solution

Calculating molarity (M) convert mass of solute (g) to mol using molar mass convert volume of solution to L use formula: M = mols solute literssolution

Example 1 What is the molarity of 2.3 moles of sodium chloride in 0.45 liters of solution? M = mols solute literssolution M = 2.3 mol = 5.1 M 0.45 L

Example 2 What is molarity of a solution prepared by dissolving 37.94 g of KOH in H2O, then diluting the volume to 500 mL? mass = 37.94 g KOH 1 mol KOH = 0.676mol 56.11 g KOH molar mass KOH volume = 500 mL 1 L = 0.500 L 1000 mL molarity = 0.676 mol = 1.35 M 0.500 L

Dilutions stock solution – mixture w/ high concentration of solute; can be diluted by adding additional solvent to get molarity needed use this equation to solve for unknown: M1 · V1 = M2 · V2

Example What is the molarity of a solution that is made by diluting 50.0 mL of 4.74 M solution of HCl to 250.0 mL? M1 = 4.74 M V1 = 50.0 mL M2 = ? V2 = 250.0 mL M1V1 = M2V2 M2 = 0.948 M

“Like dissolves like” Rule Polar solvents dissolve ionic and polar solutes partial positive & negative charges of polar molecules are attractive to one another Due to an uneven sharing of electrons in a molecule polar solvents with partial + and – charges are attracted to + and – ions in ionic compounds Nonpolar solvents dissolve nonpolar solutes http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/molvie1.swf

The Uniqueness of Water! Structure of H2O Lewis Dot Structure VSEPR Shape Electronegativity (H=2.1 and O=3.5) Hydrogen bonding

Physical Properties of Water Density of Ice Universal Solvent High melting and boiling points Cohesion (surface tension) Adhesion (capillary action) High specific heat (ability to hold heat) ALL OF THESE ARE DUE TO THE STUCTURE OF WATER (polar and hydrogen bonds)!!!