Ch. 4 Reactions in Aqueous Solution- Aqueous solution: Solution in which water is the dissolving medium4.1 General Properties of Aqueous Solutions- Solution: Homogenous mixture of two or more substances- Solvent: Substance present in greatest quantity- Solutes: Substances dissolved in solventElectrolytes and Nonelectrolytes:- Pure water is poor conductor of electricity, as water’s conductivity comes from dissolved substances.- Salt solutions is good conductor of electricityo Electric current (flow of electrically charged particles) between two electrodes of solution- More ions= greater conductivity- Electrolyte: Substances whose aqueous solutions contain ions- Nonelectrolyte: Substance that does not form ions in solutionHow Compounds Dissolve in Water:- Ionic solids dissociate into their component ions as they dissolve.- Water is effective solvent for ionic cmpds bc of partial neg. charge on O and partial pos. charge on H.- As ionic cmpds dissolve, ions become surrounded, or solvated, by H2O molecules.o “aq” denotes solvated ions- Solvation: Helps stabilize ions in solution and prevents cations and anions from recombining- Ions dispersed uniformly in solution- Nature of ions predicted from chemical name of substance (ex. Na2SO4= Na+ and SO42-)- Molecular cmpds like sucrose or methanol usually stay as intact molecules when dissolved in water.o Most are nonelectrolytes.o Acids can ionize, although they are molecular cmpdsStrong and Weak Electrolytes:- Strong electrolytes: Solutes that exist in solution completely or nearly completely as ions.o All water-soluble ionic cmpds and few molecular- Weak electrolytes: Solutes that exist in solution mostly in form of neutral molecules with small fraction in form of ionso Ex. acetic acid- Solubility is not related to ionization.- In equation, half-arrows pointing in opp. directions mean rxn is significant in both directions.o Balance of sides determines relative numbers of ions and neutral molecules- Chemical equilibrium: State in which the relative numbers of each type of ion or molecule in therxn are constant over time- Single reaction arrow used for rxns that largely go forward.o Ex. HCl ionizes, but H+ and Cl- ions do not tend to combine to form HCl- Ionic cmpds with ammonium ions are not strong electrolytes.4.2 Precipitation Reactions- Precipitation reactions: Reactions that result in the formation of a insoluble solido Occurs when pairs of opp. charged ions attract each other so strongly that they form insoluble ionic solid- Precipitate: Insoluble solid formed by a rxn in a sol’nSolubility Guidelines for Ionic Compounds:- Solubility: The amount of a certain substance that can be dissolved in a given quantity of solventat the given temp.- Any substance with solubility less than 0.01 mol/L considered insoluble in book.o Attraction between ions too strong for water to separate ions- All ionic compounds with NO3-, group 1 elements, and ammonium are soluble in water.- To predict whether precipitate forms when strong electrolyte solutions are mixedo Note ions present in reactantso Consider cation-anion combinationso Determine if combinations are insoluble- Table 4.1 Solubility GuidelinesExchange (Metathesis) Reactions:- Equation can be balanced only after chemical formulas of the products have been determined.-- Exchange reactions/ metathesis reactions: Reactions in which cations and anions appear to exchange partners- To complete and balance equationo Use chemical formulas of reactants to determine present ionso Write chemical formulas of products by combining cation from one reactant with anion from other, using ionic charges to determine subscriptso Check water solubilities of products; precipitation rxns require at least one product to beinsoluble in watero Balance equationIonic Equations and Spectator Ions:- Indicate whether dissolved substances are present predominantly as ions or as molecules.- Molecular equation: Equation which shows chemical formulas without indicating ionic character- Complete ionic equation: Equation written with all soluble strong electrolytes as ions- Spectator ions: Ions that appear in identical forms on both sides of a complete ionic equation- Net ionic equation’; Equation which includes only ions and molecules directly involved in the rxn(not repeated on both sides of equation)-Sum of ionic charges must be same-If every ion in complete ionic equation is a spectator, no rxn occurs.-Net ionic equation demonstrates more than one set of reactants can lead to same net rxn.-Steps for writing net ionic equations:o Write balanced molecular equation for rxno Rewrite equation to show ions that form in solution when each soluble strong electrolyte dissociates into its ions. Only strong electrolytes dissolved in aqueous sol’n written in ionic form.o Identify and cancel spectator ions.4.3 Acids, Bases, and Neutralization ReactionsAcids:- Acids: Substances that ionize in aqueous solution to form hydrogen ions H+ (aq)- Proton donors- Molecules of different acids ionize to form different numbers of H+ ions.- Monoprotic: Acids that yield one H+ per molecule of acid (ex, HCl, HNO3)- Diprotic: Acids that yield two H+ per molecule of acid (ex. H2SO4)o Ionization occurs in two steps.o Often only first ionization complete, so mixture of ions- Only one H+ released from acetic acid (bonded to COOH group)Bases:- Bases: Substances that accept (react w/) H+ ions- Produce hydroxide ions (OH-) in water- Bases do not have to contain OH- ions (ex. NH3).Strong and Weak Acids and Bases:- Acids and bases that are strong electrolytes are strong acids and strong bases.- Weak electrolytes are weak acids and weak bases.- Strong acids more reactive when reactivity depends only on H+ (aq) concentration- Reactivity of acid can depend on anion in addition to H+ (aq), (ex. HF reactive due to anion)- Most common strong bases are common soluble metal hydroxides.- Most common weak base is NH3.Identifying Strong and Weak Electrolytes:- All soluble ionic compounds are strong electrolytes.- Molecular compoundso Strong acids and bases are strong electrolytes, weak acids and bases are weak electrolytes, and all other compounds are nonelectrolytes.Neutralization Reactions and Salts:- Acids have sour taste and bases have bitter taste.- Acids change colors of dyes differently from bases.- Neutralization reaction: Reaction when solution of an acid and a solution of base are mixedo Products do not have characteristics of acid or base.o Between acid