CHAPTER 4OverviewIonic Thory of SolutionsAqueous Reactions and Net Ionic EquationsPrecipitation ReactionsSolubility RulesMetathesis Reaction (cont.)Acids, Bases, and SaltsPolyprotic acids and weak basesStrong and Weak Acids and BasesNeutralization ReactionOxidation – ReductionOxidation NumberDisplacement Reactions: Activity series of the elementsBalancing: Oxidation-Number MethodBalancing: Half-Reaction MethodSolution Composition, MolarityIon Concentrations in SolutionsMass % To MolarityDILUTIONSREACTIONS IN SOLUTIONTITRATIONSJohn A. SchreifelsChemistry 211-notes 1CHAPTER 4Chemical ReactionsJohn A. SchreifelsChemistry 211-notes 2Overview•Ions in Aqueous Solution–Ion theory in solutions; precipitation reactions–Molecular and ionic equation•Typical Reactions–Precipitation–Acid-Base–Oxidation-Reduction (Balancing)•Working with solutions•Quantitative analysisJohn A. SchreifelsChemistry 211-notes 3Ionic Thory of Solutions•Pure water is a very poor conductor of electricity.•Solutions from dissolving NaCl or KCl in water are very conductive.•Solutions from dissolving substances such as sugar (sucrose) C12H22O11 are non-conductive. •Electrolyte: substance that produces ions when dissolved in water.–Strong- good electrical conductor when dissolved in water (completely ionized). E.g. NaCl, KNO3, Mg(NO3)2, etc.–Weak-poor conductor when dissolved in water (partial ionization):•Non-electrolyte: substance that does not produce ions when dissolved in water.)aq(Cl)aq(Na)s(NaClOH 2  OH)aq(NH)l(OH)aq(NH423John A. SchreifelsChemistry 211-notes 4Aqueous Reactions and Net Ionic EquationsThree forms for writing chemical reaction:• Molecular: : –AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq).• Ionic: –Spectator ions are not directly involved in the reaction•Net ionic: exclude spectator ions:–Ag+(aq) + Cl(aq)  AgCl(s).AgCl(s)(aq)3NO(aq)Na(aq)Cl(aq)Na(aq)3NO(aq)Ag John A. SchreifelsChemistry 211-notes 5Precipitation Reactions•Metathesis reaction: reaction in which two substances react through exchange of their components. Driving force is often a precipitation. AX + BY  AY + BX E.g. Predict if precipitation occurs for the mixture: AgNO3(aq) + KI(aq) NaClO4(aq) + Pb(NO3)2(aq)Na2SO4(aq) + BaCl2(aq),Ni(NO3)2(aq) + (NH4)2S(aq) Hint: Use the solubility rules to determine if either product is insoluble.John A. SchreifelsChemistry 211-notes 6Solubility RulesRule ExceptionSolubleGroup 1 elements, NH4+NO3 , ClO3, ClO4 Chlorides, bromides, iodides Ag+, Pb2+, Hg22+Acetates Ag+, Hg22+Sulfates Sr2+, Ba2+, Pb2+, Ca2+ Insoluble Compounds Carbonates, phosphates, oxalates, chromates, sulfides Group 1, NH4+Hydroxides, oxides Group 1, Ba2+John A. SchreifelsChemistry 211-notes 7Metathesis Reaction (cont.) Driving force is•sometimes formation of weak or non – electrolyte.E.g. acid – base reactionsCuO(s) + 2HNO3(aq)  Cu(NO3)2(aq) + H2O(l)–CuO is normally insoluble in water, but readily dissolves in aqueous nitric acid. •sometimes formation of gas; –most common is CO2 from carbonates or H2S from sulfidesE.g. CuCO3(s) + 2HNO3(aq)  CO2(g) + Cu(NO3)2(aq) + H2O(l)CuS(s) + 2HNO3(aq)  Cu(NO3)2(aq) + H2S(g)John A. SchreifelsChemistry 211-notes 8Acids, Bases, and SaltsArrhenius definition most often used: •Acid = a hydrogen containing compound that releases hydrogen ions (H+) in solution. –HA(aq) + H2O(l)  H3O+(aq) + A(aq) where •HA = HCl, HNO3,etc. and •H3O+ = hydronium ion often written as H+. •Base = compound that releases hydroxide ions (OH) in solution. The general reaction for a base is:–MOH(s)  OH(aq) + M+(aq) where •M = some metal such as Na, K, etc. •Acids and bases can be strong or weak electrolytes. •A base/acid that is a strong electrolyte is a strong base/acid.John A. SchreifelsChemistry 211-notes 9Polyprotic acids and weak bases•Some acids have more than one acidic proton. –Sulfuric:–Phosphoric:•Most weak bases produce hydroxide ions by reaction with water. –Ammonia(aq)O3H(aq)4SO O(l)2H (aq)4HSO(aq)O3H(aq)4HSO O(l)2H (l)4SO2H2(aq)O3H(aq)4PO O(l)2H (aq)4HPO(aq)O3H(aq)4HPO O(l)2H (aq)4PO2H(aq)O3H(aq)4PO2H O(l)2H (l)4PO3H322)aq(OH)aq(NHOH)aq(NH423John A. SchreifelsChemistry 211-notes 10Strong and Weak Acids and Bases•Organic acids are weak (usually have –COOH).•Amines (containing nitrogen) are weak.•In water they are completely dissociated:–HCl(aq) + H2O(l)  H3O+(aq) + Cl(aq)Strong Acids Strong BasesChloric, HClO3Grp 1A hydroxides (LiOH, NaOH, KOH, RbOH, CsOH)Hydrobromic, HBrHydroiodic, HI Grp 2A metal hydroxides (Ca(OH)2, Sr(OH)2, Ba(OH)2Perchloric, HClO4Sulfuric, H2SO4Nitric, HNO3John A. SchreifelsChemistry 211-notes 11Neutralization Reaction•Acids react with bases to form a salt and possibly water (called the neutralization reaction):–HA(aq)+MOH(aq)M+(aq)+A(aq)+H2O(l).–If either the acid or base is a strong electrolyte, exclude spectator ions in the ionic form. E.g. HCN = weak acid; NaOH = strong base; neutralization reaction is–HCN(aq) + OH(aq)  CN(aq) + H2O(l)Eg. 2 HCl neutralized by NaOH; net ionic equation:–H+(aq) + OH(aq)  H2O(l)John A. SchreifelsChemistry 211-notes 12Oxidation – Reduction•Oxidation = loss of at least one electron during a reaction..–Ni(s) + H+(aq)  Ni2+(aq) + H2(g)•Reduction = gain of at least one electron during a reaction.–In above example, H+ gains an electron to become reduced.•Every reaction must have an oxidation and reduction.•Metals react with acids to form salts and hydrogen gas.–Cu(s) + 2HNO3(aq)  Cu(NO3)2(aq) + H2(g)•Metals also oxidized with salts–Fe(s) + Cu(NO3)2(aq)  Fe(NO3)2(aq) + Cu(s)John A. SchreifelsChemistry 211-notes 13Oxidation Number•Oxidation number (state): the charge on an atom in a substance or monatomic ion.•Rules:–Elemental form: 0–Monatomic ions: charge of ion–Oxygen: 2, except in H2O2 and other peroxides.–Hydrogen: +1, except with metal hydrides when it is 1.–Halogens: 1 (except when bound to oxygen or a halide above it)–Alkali and alkaline earth metal ions have a charge of +1 and +2, respectively.–Compounds and ions: sum of the charges on the atoms in a compound add up to 0 and to the ion charge in the ion.Ca in CaO +2Ca2+(aq)