5pure H2O, sugar solution, glycerol ElectrolytesStrong - conduct current efficiently - many ions in solution.NaCl, KNO3, HNO3, NaOHWeak - conduct only a small current - few ions in solution,HC2H3O2, aq. NH3, tap H2ONon - no current flows - no ions in solution.pure H2O, sugar solution, glycerol
6In what two ways can a solid ionic compound be made to conduct electricity? Dissolve it in water.Melt or fuse it.Ions must be free to move(mobile) in order to conduct electricity!
7Dissociation ionic compounds metal + nonmetal (Type I & II)metal + polyatomic anionAmmonium compoundsAcidsWhen ionic compounds dissolve in water the anions and cations are separated from each other; this is called dissociationWe know that ionic compounds dissociate when they dissolve in water because the solution conducts electricity4
8Dissociationpotassium chloride dissociates in water into potassium cations and chloride anionsKCl(aq) = K+ (aq) + Cl- (aq)copper(II) sulfate dissociates in water into copper(II) cations and sulfate anionsCuSO4(aq) = Cu+2(aq) + SO42-(aq)K+Cl-KClCu+2SO42-CuSO45
9K2SO4(aq) = 2 K+ (aq) + SO42-(aq) Dissociationpotassium sulfate dissociates in water into potassium cations and sulfate anionsK2SO4(aq) = 2 K+ (aq) + SO42-(aq)K+SO42-KSO46
10Ionic Compounds in Solution In aqueous solution, soluble ionic compoundsexist in the form of ions.K2CrO4(aq) + Ba(NO3)2(aq) ----> BaCrO4(s) + 2KNO3(aq)
11Figure 7.1: The precipitation reaction that occurs when yellow potassium chormate, K2CrO4 (aq), is mixed with a colorless barium nitrate solution, Ba(NO3)2 (aq)
12Solubility1. A soluble solid readily dissolves in water-- designated with (aq).2. A slightly soluble solid only dissolves to a tiny extent in water--designated with (s).3. An insoluble solid does not dissolve to any appreciable extent in water--designated with (s).
13Simple Rules for Solubility 1. Most nitrate (NO3), acetate (C2H3O2-), & chlorate (ClO3-) salts are soluble.2. Most alkali (group 1A) salts and NH4+ are soluble.3. Most Cl, Br, and I salts are soluble (NOT Ag+, Pb2+, Hg22+)4. Most sulfate salts are soluble (NOT BaSO4, PbSO4, HgSO4, CaSO4)5. Most OH salts are only slightly soluble (NaOH, KOH are soluble, Ba(OH)2, Ca(OH)2 are marginally soluble)6. Most S2, CO32, CrO42, PO43 salts are only slightly soluble.
15Precipitation Reactions In all precipitation reactions, the ions of one substance are exchanged with the ions of another substance when their aqueous solutions are mixedAt least one of the products formed is insoluble in waterKI(aq) + AgNO3(aq) KNO3(aq) + AgIsK+I-Ag+NO3-AgI3
16Describing Reactions in Solution 1. Molecular equation (reactants and products as compounds)AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)2. Complete ionic equation (all strong electrolytes shown as ions)Ag+(aq) + NO3(aq) + Na+(aq) + Cl(aq) AgCl(s) + Na+(aq) + NO3(aq)
17Describing Reactions in Solution (continued) 3. Net ionic equation (show only components that actually react)Ag+(aq) + Cl(aq) AgCl(s)Na+ and NO3 are spectator ions.
21Acids The nature of acids was discovered by Svante Arrhenius. Acids are characterized by:a sour taste (lemons -- citric acid).producing H+ ions (protons) in aqueous solution.turn blue litmus red.
22AcidsStrong acids - dissociate completely (nearly 100 %) to produce H+ in solutionHCl, H2SO4, HNO3, HBr, HI, & HClO4Weak acids - dissociate to a slight extent (approximately 1 %) to give H+ in solutionHC2H3O2, HCOOH, HNO2, & H2SO3
23Figure 7.5: When gaseous HCl is dissolved in water, each molecule dissociates to produce H+ and Cl- ions
24Bases Bases are characterized by: bitter taste (soap). feel slippery. produce hydroxide (OH-) ions in aqueous solution.turn red litmus blue.A basic solution is said to be alkaline since they often contain one of the alkali metals --Na, K, Li, etc.
25Bases Strong bases - react completely with water to give OH ions. sodium hydroxideWeak bases - react only slightly with water to give OH ions.ammonia
26Acid + Base ----> Salt + water Acid-Base ReactionsAcid + Base ----> Salt + waterMolecular EquationHCl(aq) + NaOH(aq) ----> NaCl(aq) + HOH(l)Complete Ionic EquationH+(aq) + Cl-(aq) + Na+(aq) + OH-(aq) -----> Na+(aq) + Cl-(aq)+ HOH(l)Net Ionic EquationH+(aq) + OH-(aq) -----> HOH(l)
27Acid-Base Neutralization The net ionic equation for the neutralization of any strong acid and base will always be:H+(aq) + OH-(aq) -----> HOH(l)
28Salts Salts are ionic compounds consisting of: a. metal & nonmetal -- KClb. metal & polyatomic ion -- CuSO4c. polyatomic ion & nonmetal -- NH4Cld. two polyatomic ions -- (NH4)2SO4
29Oxidation-Reduction Reactions (Redox Reactions) Redox reaction -- involves the transfer of electronsloss and gain of electrons must be exactly equal.loss and gain of electrons must be simultaneous.
30Oxidation loss of electrons metal atoms -- Na, Ca, & K Nao ---> Na1+ + 1e-Cao ---> Ca2+ + 2e-nonmetal ions -- Cl-, S2-, & O2-Cl1- ---> Clo + 1e-S2- ---> So + 2 e-
31Reduction gain of electrons. nonmetal atoms. Oo + 2e- ---> O2- Fo + 1e- ---> F1-metal ions.K1+ + 1e- ---> KoBa2+ + 2e- ---> Bao
32Figure 7.7: When powdered aluminum and iodine (shown in the foreground) are mixed (and a little water added), they react vigorously
33Oxidation & Reduction Half-Reactions Always add electrons (negative) to the more positive side of the equation.The charge on both sides of an equation must be equal.Oxidation -- Nao ----> Na e-Reduction -- Cl2 + 2 e- ----> 2 Cl-
35Redox Reactions Metal-nonmetal reactions are always redox reactions. Any reaction that has a free element (such as O2) as a reactant or product are redox.All single replacement reactions are redox.All combustion reactions are redox.
36Synthesis I (Composition) A + X ----> AX ALWAYS REDOXElement + Element -----> Binary CompoundFe(s) + S(s) ----> FeS(s)4 Al(s) + 3 O2(g) ----> 2 Al2O3(s)
37Synthesis II (Composition) A + X ----> AX NOT REDOXCompound + Compound ----> Compound ( or more elements)Ammonia + Acid ----> Ammonium SaltNH3(g) + HCl(g) ----> NH4Cl(s)2 NH3(aq) + H2SO4(aq) ----> (NH4)2SO4(aq)
38Synthesis II (Composition) Continued Water + An OxideRule # 1 --Water + Metal Oxide ----> Metal Hydroxide (Base)HOH(l) + CaO(s) ----> Ca(OH)2(s)HOH(l) + Na2O(s) ----> 2 NaOH(aq)Rule # 2 --Water + Nonmetal Oxide ----> AcidHOH(l) + SO3(g) ----> H2SO4(aq)HOH(l) + N2O5(g) ----> 2 HNO3(aq)
39Single Replacement I A + BX ----> AX + B ALWAYS REDOX Element + Compound ----> Different Element Different CompoundMetal Reactivities:K > Na > Ca > Mg > Al > Zn > Cr > Fe > Cd > Co > Ni > Sn > Pb > H > Sb > Cu > Hg > Ag > Pt > Au
40Single Replacement I (Continued) A is a metal.A is more reactive than BA + BX ----> AX + BCu(s) + 2 AgNO3(aq) ---->Cu(NO3)2(aq) + 2 Ag(s)Zn(s) + 2 HCl(aq) ----> ZnCl2(aq) + H2(g)Rule # 3 -- Active Metal + Water ----> Metal Hydroxide + HydrogenCa(s) + 2 HOH(l) ----> Ca(OH)2(s) + H2(g)
41Single Replacement I (Continued) A is a metal.A is less reactive than BA + BX ----> No Reaction (NR)Cu(s) + HCl(aq) ----> NR
42Single Replacement II Y + BX ----> BY + X ALWAYS REDOX Element + Compound ----> Different Element Different CompoundNonmetal Reactivities:F > O > Cl > Br > I
43Single Replacement II (Continued) Y is a nonmetal.Y is more reactive than XY + BX ----> BY + XCl2(g) + 2 KBr(aq) ----> 2 KCl(aq) + Br2(aq)Y is less reactive than XY + BX ----> No ReactionCl2(g) + KF(aq) ----> NR