Transcript solute
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/36d8205 07a4c220061eb/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) 1. 2. 3. convert mass of solute (g) to mol using molar mass convert volume of solution to L use formula: mols solute M= literssolution Example 1 – What is the molarity of 2.3 moles of sodium chloride in 0.45 liters of solution? mols solute M= 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 I. I. partial positive & negative charges of polar molecules are attractive to one another I. Due to an uneven sharing of electrons in a molecule II. polar solvents with partial + and – charges are attracted to + and – ions in ionic compounds II. Nonpolar solvents dissolve nonpolar solutes http://www.mhhe.com/physsci/chemistry/essen tialchemistry/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)!!!