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Slide 1 ___________________________________ ___________________________________ ___________________________________ Reactions in Aqueous Solution ___________________________________ Chapter 4 ___________________________________ ___________________________________ For test 3: Sections 3.7 and 4.1 to 4.5 ___________________________________ Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Slide 2 ___________________________________ A solution is a homogenous mixture of 2 or more substances ___________________________________ The solute is(are) the substance(s) present in the smaller amount(s) ___________________________________ The solvent is the substance present in the larger amount ___________________________________ ___________________________________ Solution Solvent Solute Soft drink(l) H2O Sugar, CO2 Air(g) N2 O2, Ar, CH4 Soft Solder(s) Pb Sn ___________________________________ aqueous solutions of KMnO4 ___________________________________ 2 Slide 3 ___________________________________ An electrolyte is a substance that, when dissolved in water, results in a solution that can conduct electricity. ___________________________________ A nonelectrolyte is a substance that, when dissolved, results in a solution that does not conduct electricity. ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ nonelectrolyte weak electrolyte strong electrolyte 3 Slide 4 ___________________________________ Conduct electricity in solution? ___________________________________ Cations (+) and Anions (-) ___________________________________ Strong Electrolyte – 100% dissociation NaCl(s) H2O ___________________________________ Na+(aq) + Cl-(aq) ___________________________________ Weak Electrolyte – not completely dissociated CH3COOH ___________________________________ CH3COO-(aq) + H+(aq) ___________________________________ 4 Slide 5 ___________________________________ Ionization of acetic acid ___________________________________ CH3COOH CH3COO-(aq) + H+(aq) ___________________________________ ___________________________________ A reversible reaction. The reaction can occur in both directions. ___________________________________ ___________________________________ Acetic acid is a weak electrolyte because its ionization in water is incomplete. ___________________________________ 5 Slide 6 ___________________________________ Hydration is the process in which an ion is surrounded by water molecules arranged in a specific manner. ___________________________________ ___________________________________ ___________________________________ ___________________________________ d- ___________________________________ ___________________________________ d+ H2O 6 Slide 7 ___________________________________ Nonelectrolyte does not conduct electricity? ___________________________________ No cations (+) and anions (-) in solution C6H12O6(s) H2O ___________________________________ C6H12O6(aq) ___________________________________ ___________________________________ ___________________________________ ___________________________________ 7 Slide 8 A process in which one or more substances is changed into one or more new substances is a chemical reaction A chemical equation uses chemical symbols to show what happens during a chemical reaction reactants ___________________________________ ___________________________________ ___________________________________ products 3 ways of representing the reaction of H2 with O2 to form H2O ___________________________________ ___________________________________ ___________________________________ ___________________________________ From Chapter 3 section 3.7 Slide 9 8 ___________________________________ How to “Read” Chemical Equations ___________________________________ 2 Mg + O2 2 MgO ___________________________________ 2 atoms Mg + 1 molecule O2 makes 2 formula units MgO ___________________________________ 2 moles Mg + 1 mole O2 makes 2 moles MgO 48.6 grams Mg + 32.0 grams O2 makes 80.6 g MgO NOT ___________________________________ 2 grams Mg + 1 gram O2 makes 2 g MgO From Chapter 3 section 3.7 ___________________________________ ___________________________________ 9 Slide ___________________________________ Balancing Chemical Equations 10 ___________________________________ 1. Write the correct formula(s) for the reactants on the left side and the correct formula(s) for the product(s) on the right side of the equation. ___________________________________ Ethane reacts with oxygen to form carbon dioxide and water ___________________________________ C2H6 + O2 CO2 + H2O ___________________________________ 2. Change the numbers in front of the formulas (coefficients) to make the number of atoms of each element the same on both sides of the equation. Do not change the subscripts. 2C2H6 NOT C4H12 From Chapter 3 section 3.7 Slide ___________________________________ 10 ___________________________________ Balancing Chemical Equations 11 ___________________________________ ___________________________________ 3. Start by balancing those elements that appear in only one reactant and one product. C2H6 + O2 CO2 + H2O ___________________________________ start with C or H but not O ___________________________________ 1 carbon on right 2 carbon on left C2H6 + O2 6 hydrogen on left C2H6 + O2 Slide 12 multiply CO2 by 2 ___________________________________ 2CO2 + H2O 2 hydrogen on right 2CO2 + 3H2O ___________________________________ multiply H2O by 3 ___________________________________ 11 From Chapter 3 section 3.7 ___________________________________ Balancing Chemical Equations ___________________________________ 4. Balance those elements that appear in two or more reactants or products. C2H6 + O2 2 oxygen on left 2CO2 + 3H2O multiply O2 by 7 2 ___________________________________ 4 oxygen + 3 oxygen = 7 oxygen (3x1) on right (2x2) C2H6 + 7 O2 2 2CO2 + 3H2O 2C2H6 + 7O2 4CO2 + 6H2O ___________________________________ remove fraction multiply both sides by 2 From Chapter 3 section 3.7 ___________________________________ ___________________________________ ___________________________________ 12 Slide ___________________________________ Balancing Chemical Equations 13 ___________________________________ 5. Check to make sure that you have the same number of each type of atom on both sides of the equation. 2C2H6 + 7O2 ___________________________________ 4CO2 + 6H2O 4 C (2 x 2) 4C 12 H (2 x 6) 12 H (6 x 2) 14 O (7 x 2) 14 O (4 x 2 + 6) ___________________________________ Reactants Products ___________________________________ 4C 12 H 14 O ___________________________________ 4C 12 H 14 O From Chapter 3 section 3.7 13 Slide ___________________________________ Precipitation Reactions 14 Precipitate – insoluble solid that separates from solution precipitate Pb(NO3)2(aq) + 2NaI(aq) Pb2+ + 2NO3- + 2Na+ + 2I- PbI2(s) + 2NaNO3(aq) PbI2(s) + 2Na+ + 2NO3- ionic equation Pb2+ PbI2 + 2I- ___________________________________ ___________________________________ molecular equation ___________________________________ ___________________________________ ___________________________________ PbI2(s) ___________________________________ net ionic equation Na+ and NO3- are spectator ions 14 Slide 15 ___________________________________ ___________________________________ Precipitation of Lead Iodide ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Pb2+ + 2I- PbI2(s) PbI2 15 ___________________________________ Slide 16 Solubility is the maximum amount of solute that will dissolve in a given quantity of solvent at a specific temperature. ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ 16 Slide ___________________________________ Examples of Insoluble Compounds 17 ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ CdS PbS Ni(OH)2 Al(OH)3 17 Slide 18 ___________________________________ Writing Net Ionic Equations 1. Write the balanced molecular equation. 2. Write the ionic equation showing the strong electrolytes completely dissociated into cations and anions. ___________________________________ 3. Cancel the spectator ions on both sides of the ionic equation 4. Check that charges and number of atoms are balanced in the net ionic equation Write the net ionic equation for the reaction of silver nitrate with sodium chloride. AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq) Ag+ + NO3- + Na+ + Cl- AgCl(s) + Na+ + NO3- Ag+ + Cl- AgCl(s) 18 ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Slide Properties of Acids ___________________________________ Have a sour taste. Vinegar owes its taste to acetic acid. Citrus fruits contain citric acid. ___________________________________ Cause color changes in plant dyes. ___________________________________ 19 React with certain metals to produce hydrogen gas. 2HCl(aq) + Mg(s) ___________________________________ MgCl2(aq) + H2(g) ___________________________________ React with carbonates and bicarbonates to produce carbon dioxide gas 2HCl(aq) + CaCO3(s) ___________________________________ CaCl2(aq) + CO2(g) + H2O(l) Aqueous acid solutions conduct electricity. ___________________________________ 19 Slide ___________________________________ Properties of Bases 20 ___________________________________ Have a bitter taste. ___________________________________ Feel slippery. Many soaps contain bases. Cause color changes in plant dyes. ___________________________________ Aqueous base solutions conduct electricity. ___________________________________ Examples: ___________________________________ ___________________________________ 20 Slide 21 ___________________________________ Arrhenius acid is a substance that produces H+ (H3O+) in water ___________________________________ ___________________________________ ___________________________________ Arrhenius base is a substance that produces OH- in water ___________________________________ ___________________________________ ___________________________________ 21 Slide ___________________________________ Hydronium ion, hydrated proton, H3O+ 22 ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ 22 Slide ___________________________________ A Brønsted acid is a proton donor A Brønsted base is a proton acceptor 23 ___________________________________ ___________________________________ ___________________________________ ___________________________________ base acid acid base ___________________________________ A Brønsted acid must contain at least one ionizable proton! ___________________________________ 23 Slide 24 ___________________________________ Monoprotic acids HCl H+ + Cl- HNO3 H+ + Strong electrolyte, strong acid NO3H+ CH3COOH + Strong electrolyte, strong acid CH3COO- Weak electrolyte, weak acid Diprotic acids H2SO4 HSO4- H+ + SO42- + HSO4- Strong electrolyte, strong acid Weak electrolyte, weak acid Triprotic acids H3PO4 H2PO4HPO42- ___________________________________ ___________________________________ H+ H+ ___________________________________ + H2PO4H+ + HPO42H+ + PO43- ___________________________________ ___________________________________ Weak electrolyte, weak acid Weak electrolyte, weak acid Weak electrolyte, weak acid 24 ___________________________________ Slide 25 ___________________________________ Identify each of the following species as a Brønsted acid, base, or both. (a) HI, (b) CH3COO-, (c) H2PO4- ___________________________________ ___________________________________ H+ (aq) + I- (aq) HI (aq) Brønsted acid ___________________________________ CH3COO- H+ (aq) + (aq) CH3COOH (aq) Brønsted base ___________________________________ H2PO4- (aq) H2PO4- H+ (aq) + HPO42- (aq) (aq) + H+ (aq) H3PO4 (aq) Brønsted acid ___________________________________ Brønsted base ___________________________________ 25 Slide 26 ___________________________________ Neutralization Reaction ___________________________________ acid + base salt + water ___________________________________ ___________________________________ HCl(aq) + NaOH(aq) NaCl(aq) + H2O H+ + Cl- + Na+ + OH- Na+ + Cl- + H2O H+ + OH- ___________________________________ ___________________________________ H2O ___________________________________ 26 Slide 27 Neutralization Reaction Involving a Weak Electrolyte weak acid + base salt + water ___________________________________ ___________________________________ ___________________________________ ___________________________________ HCN(aq) + NaOH(aq) HCN + Na+ + OHHCN + OH- NaCN(aq) + H2O ___________________________________ Na+ + CN- + H2O ___________________________________ CN- + H2O ___________________________________ 27 Slide ___________________________________ Neutralization Reaction Producing a Gas 28 ___________________________________ acid + base 2HCl(aq) + Na2CO3(aq) salt + water + CO2 ___________________________________ 2NaCl(aq) + H2O +CO2 ___________________________________ ___________________________________ 2H+ + 2Cl- + 2Na+ + CO322H+ + CO32- 2Na+ + 2Cl- + H2O + CO2 ___________________________________ H2O + CO2 ___________________________________ 28 Slide Oxidation-Reduction Reactions 29 (electron transfer reactions) ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ 2Mg2+ + 4e- Oxidation half-reaction (lose e-) O2 + 4e2O2Reduction half-reaction (gain e-) 2Mg + O2 + 4e2Mg2+ + 2O2- + 4e29 2Mg + O2 2MgO 2Mg Slide ___________________________________ ___________________________________ ___________________________________ 30 ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ 30 Slide ___________________________________ 31 Zn(s) + CuSO4(aq) ZnSO4(aq) + Cu(s) Zn2+ + 2e- Zn is oxidized Zn Cu2+ + 2e- ___________________________________ Zn is the reducing agent Cu Cu2+ is reduced Cu2+ is the oxidizing agent ___________________________________ Copper wire reacts with silver nitrate to form silver metal. What is the oxidizing agent in the reaction? Cu(s) + 2AgNO3(aq) Cu2+ Cu Ag+ + 1e- + ___________________________________ ___________________________________ Cu(NO3)2(aq) + 2Ag(s) ___________________________________ 2e- Ag Ag+ is reduced Ag+ is the oxidizing agent ___________________________________ 31 Slide 32 ___________________________________ Oxidation number ___________________________________ The charge the atom would have in a molecule (or an ionic compound) if electrons were completely transferred. ___________________________________ 1. Free elements (uncombined state) have an oxidation number of zero. ___________________________________ Na, Be, K, Pb, H2, O2, P4 = 0 ___________________________________ 2. In monatomic ions, the oxidation number is equal to the charge on the ion. ___________________________________ Li+, Li = +1; Fe3+, Fe = +3; O2-, O = -2 ___________________________________ 3. The oxidation number of oxygen is usually –2. In H2O2 and O22- it is –1. 32 Slide 33 4. The oxidation number of hydrogen is +1 except when it is bonded to metals in binary compounds. In these cases, its oxidation number is –1. 5. Group IA metals are +1, IIA metals are +2 and fluorine is always –1. 6. The sum of the oxidation numbers of all the atoms in a molecule or ion is equal to the charge on the molecule or ion. 7. Oxidation numbers do not have to be integers. Oxidation number of oxygen in the superoxide ion, O2-, is –½. - HCO3 What are the oxidation numbers of all the elements in HCO3- ? O = –2 ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ H = +1 3x(–2) + 1 + ? = –1 C = +4 4.4 33 ___________________________________ Slide The Oxidation Numbers of Elements in their Compounds 34 ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ 34 Slide 35 ___________________________________ IF7 What are the oxidation numbers of all the elements in each of these compounds? NaIO3 IF7 K2Cr2O7 ___________________________________ F = -1 7x(-1) + ? = 0 ___________________________________ I = +7 NaIO3 ___________________________________ Na = +1 O = -2 ___________________________________ K2Cr2O7 3x(-2) + 1 + ? = 0 O = -2 I = +5 K = +1 ___________________________________ 7x(-2) + 2x(+1) + 2x(?) = 0 ___________________________________ Cr = +6 35 Slide 36 ___________________________________ Types of Oxidation-Reduction Reactions ___________________________________ Combination Reaction A+ B 0 0 3Mg + N2 ___________________________________ C +2 -3 ___________________________________ MgN2 ___________________________________ Decomposition Reaction C +1 +5 -2 2KClO3 A+ B +1 -1 ___________________________________ ___________________________________ 0 2KCl + 3O2 36 Slide 37 ___________________________________ Types of Oxidation-Reduction Reactions ___________________________________ Combustion Reaction ___________________________________ A + O2 B 0 ___________________________________ +4 -2 0 S + O2 SO2 ___________________________________ ___________________________________ 0 +2 -2 0 2Mg + O2 2MgO ___________________________________ 37 Slide 38 ___________________________________ Types of Oxidation-Reduction Reactions ___________________________________ Displacement Reaction ___________________________________ A + BC 0 +1 +2 Sr + 2H2O +4 0 TiCl4 + 2Mg 0 AC + B -1 Cl2 + 2KBr ___________________________________ 0 Sr(OH)2 + H2 Hydrogen Displacement 0 ___________________________________ +2 Ti + 2MgCl2 -1 Metal Displacement ___________________________________ 0 2KCl + Br2 Halogen Displacement ___________________________________ 38 Slide 39 ___________________________________ The Activity Series for Metals ___________________________________ Hydrogen Displacement Reaction M + BC ___________________________________ MC + B ___________________________________ M is metal BC is acid or H2O B is H2 ___________________________________ Ca + 2H2O Ca(OH)2 + H2 Pb + 2H2O Pb(OH)2 + H2 39 ___________________________________ ___________________________________ Slide 40 ___________________________________ The Activity Series for Halogens ___________________________________ F2 > Cl2 > Br2 > I2 ___________________________________ Halogen Displacement Reaction 0 -1 Cl2 + 2KBr I2 + 2KBr -1 0 2KCl + Br2 2KI + Br2 ___________________________________ ___________________________________ ___________________________________ ___________________________________ 40 Slide 41 ___________________________________ Classify each of the following reactions. Ca2+ + CO32- NH3 + H+ Zn + 2HCl Ca + F2 CaCO3 NH4+ ZnCl2 + H2 CaF2 ___________________________________ Precipitation ___________________________________ Acid-Base ___________________________________ Redox (H2 Displacement) ___________________________________ Redox (Combination) ___________________________________ ___________________________________ 41 Slide 42 ___________________________________ Gravimetric Analysis ___________________________________ 1. Dissolve unknown substance in water 2. React unknown with known substance to form a precipitate ___________________________________ 3. Filter and dry precipitate 4. Weigh precipitate ___________________________________ 5. Use chemical formula and mass of precipitate to determine amount of unknown ion ___________________________________ ___________________________________ ___________________________________ 42 Slide 43 ___________________________________ Titrations In a titration a solution of accurately known concentration is added gradually added to another solution of unknown concentration until the chemical reaction between the two solutions is complete. ___________________________________ ___________________________________ Equivalence point – the point at which the reaction is complete ___________________________________ Indicator – substance that changes color at (or near) the equivalence point ___________________________________ Slowly add base to unknown acid UNTIL ___________________________________ ___________________________________ the indicator changes color 43 Slide ___________________________________ Titrations can be used in the analysis of 44 ___________________________________ Acid-base reactions ___________________________________ H2SO4 + 2NaOH 2H2O + Na2SO4 ___________________________________ ___________________________________ Redox reactions 5Fe2+ + MnO4- + 8H+ ___________________________________ ___________________________________ Mn2+ + 5Fe3+ + 4H2O 44 Slide 45 ___________________________________ CH-3 (part) and 4 HW ___________________________________ Questions and Problems Page 91 ___________________________________ 3.60 & 3.64 ___________________________________ Questions and Problems Pages 129 - 131 ___________________________________ ___________________________________ 4.8, 4.10, 4.12, 4.14, 4.18, 4.20, 4.22, 4.24, 4.32 , 4.34, 4.40, 4.42, 4.44, 4.46, 4.48, 4.50 ___________________________________ 45