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Reactions in Aqueous Solution

Reactions in Aqueous Solution. Chapter 4 Dr. Ali Bumajdad. Solution Stoichiometry. Chapter 4 Topics. Solution Electrolytes, acids and bases Precipitation reactions and solubility rules Molecular eqn., ionic eqn & net ionic eqn. Oxidation reduction reactions (Redox Reactions)

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Reactions in Aqueous Solution

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  1. Reactions in Aqueous Solution Chapter 4 Dr. Ali Bumajdad

  2. Solution Stoichiometry Chapter 4 Topics • Solution • Electrolytes, acids and bases • Precipitation reactions and solubility rules • Molecular eqn., ionic eqn & net ionic eqn. • Oxidation reduction reactions • (Redox Reactions) • Molarity and Dilution • Solution Stoichiometry (gravimetric analysis, titrations, limiting reactant….etc) Dr. Ali Bumajdad

  3. Solution Solvent Solute Solution • solution is a homogenous mixture of 2 or more substances • solute is(are) the substance(s) present in the smaller amount(s) • solvent is the substance present in the larger amount H2O Soft drink (l) Sugar, CO2 Air (g) N2 O2, Ar, CH4 Pb Sn Soft Solder (s) Dr. Ali Bumajdad

  4. strong electrolyte nonelectrolyte weak electrolyte Electrolytes, acids and bases • Electrolyte is a substance when dissolved in water results in a solution that can conduct electricity. • Why? Because it gives ion when dissolve in water • Nonelectrolyte is a substance when dissolved results in a solution that does not conduct electricity. • Why? Because it does not dissociates into ions

  5. H2O H2O H2O NaOH (l)Na+ (aq) + OH- (aq) NaCl (s)Na+ (aq) + Cl- (aq) HCl (l)H+ (aq) + Cl- (aq) CH3COOHCH3COO- (aq) + H+ (aq) NH3 + H2ONH4+ (aq) + OH- (aq) 0.1M 1% 1% Dissociation or Ionization? Cations (+) and Anions (-) • Strong Electrolyte: 100% dissociation Soluble salt Strong acid Strong Base • Weak Electrolyte: not completely dissociated Weak acid Weak base Dr. Ali Bumajdad

  6. H2O C6H12O6 (s) C6H12O6 (aq) • Non-electrolyte: No dissociation into ions Example: Sugar, ethanol (CH3CH2OH) (Note that sugar and ethanol (CH3CH2OH) soluble in water but do not gives ions when dissolved) Q) Which of the following is not a strong electrolytes: 1) KCl 6)H2SO4 11) H2O 2)LiOH 7)HCl 12) HF 3)NaNO3 8)HNO3 13)HBr 4)NH3 9)KOH 14) H3PO4 5)Suger 10)HC2H3O2 Dr. Ali Bumajdad

  7. 2HCl (aq) + Mg (s) MgCl2 (aq) + H2 (g) 2HCl (aq) + CaCO3 (s) CaCl2 (aq) + CO2 (g) + H2O (l) Acids • Have a sour taste. Vinegar owes its taste to acetic acid. Citrus • fruits contain citric acid. • React with certain metals to produce hydrogen gas. • React with carbonates and bicarbonates to produce carbon • dioxide gas • Aqueous acid solutions conduct electricity. Dr. Ali Bumajdad

  8. Bases • Have a bitter taste. • Feel slippery. Many soaps contain bases. • Aqueous base solutions conduct electricity. Dr. Ali Bumajdad

  9. Arrhenius acid is a substance that produces H+ (H3O+) in water Arrhenius base is a substance that produces OH- in water Dr. Ali Bumajdad

  10. A Brønsted acid must contain at least one ionizable proton! A Brønstedacid is a proton donor A Brønsted base is a proton acceptor base acid acid base Dr. Ali Bumajdad

  11. HCl H+ + Cl- HNO3 H+ + NO3- CH3COOH H+ + CH3COO- H2SO4 H+ + HSO4- HSO4- H+ + SO42- HPO42- H+ + PO43- H2PO4- H+ + HPO42- H3PO4 H+ + H2PO4- Monoprotic acids Strong electrolyte, strong acid Strong electrolyte, strong acid Weak electrolyte, weak acid Diprotic acids Strong electrolyte, strong acid Weak electrolyte, weak acid Triprotic acids Weak electrolyte, weak acid Weak electrolyte, weak acid Weak electrolyte, weak acid Dr. Ali Bumajdad

  12. HI (aq) H+ (aq) + I- (aq) CH3COO- (aq) + H+ (aq) CH3COOH (aq) H2PO4-(aq) H+ (aq) + HPO42- (aq) H2PO4-(aq) + H+ (aq) H3PO4 (aq) Q) Identify each of the following species as a Brønsted acid, base, or both. (a) HI, (b) CH3COO-, (c) H2PO4- Brønsted acid Brønsted base Brønsted acid Brønsted base Dr. Ali Bumajdad

  13. Acid - Base Equilibria 1 ) Arrhenius Definition: + H Acid: Substance when dissolved in water increase · - OH Base: Substance when dissolved in water increase · 2 ) BrØnsted - Lowry Definition: + Acid: Substance that donate H · + Base: Substance that accept H · 3 ) Lewis Def inition: Acid: Electron - pair acceptor · Base: Electron pair donor · Dr. Ali Bumajdad

  14. acid + base salt + water HCl (aq) + NaOH (aq) NaCl (aq) + H2O H+ + Cl- + Na+ + OH- Na+ + Cl- + H2O H+ + OH- H2O Neutralization Reaction Dr. Ali Bumajdad

  15. A weak acid is a weak electrolyte A strong acid is a strong electrolyte A weak base is a weak electrolyte A strong base is a strong electrolyte Dr. Ali Bumajdad

  16. d- d+ H2O • Hydration the process in which an ion is surrounded by water molecules Dr. Ali Bumajdad

  17. Dr. Ali Bumajdad

  18. PbI2 Precipitation reactions and solubility rules Precipitate: insoluble solid that separates from solution Dr. Ali Bumajdad

  19. All chlorides, bromides, Iodides except those of Ag+, Pb2+ and Hg22+ e.g. MgI2 All metals oxides except those of alkali metals, Ca2+, Sr2+, Ba2+ e.g. MgO cation salts 1) alkali metals salts e.g. NaCl 2) ammonium ion salts e.g. (NH4)2SO4 All hydroxides except those of alkali metals, Ca2+, Sr2+, Ba2+ e.g. Be(OH)2 All sulfates (SO42-) except those of Ag+, Ca2+, Sr2+, Ba2+ Pb2+, andHg2+ e.g. MgSO4 Anions salts 1) nitrate ion salts e.g. KNO3 2) chlorate ion salts e.g. NaClO3 3) perchlorate ion salts e.g. KClO4 4) acetate ion salts e.g. Cu(C2H3O2)2 All carbonates (CO32-), phosphates ( PO43-), sulfides (S2-) and sulfites (SO32-), and chromate (CrO42-) except those of NH4+, alkali metals e.g. CaCO3 Solubility Rules insoluble salts with exceptions Soluble salts with exceptions soluble salts Dr. Ali Bumajdad

  20. Q) Soluble or not: b) FeCO3 Not Soluble a) Na2S Soluble Not Soluble d) ZnO c) AgBr Not Soluble Not Soluble f) PbSO4 Soluble e) Cu(C2H3O2)2 g) Ni(OH)2 Not Soluble Dr. Ali Bumajdad

  21. AgNO3 (aq) + NaCl (aq) AgCl (s) + NaNO3 (aq) Ag+ + NO3- + Na+ + Cl- AgCl (s) + Na+ + NO3- Ag+ + Cl- AgCl (s) Molecular eqn., ionic eqn & net ionic eqn. Writing Net Ionic Equations • Write the balanced molecular equation. • Write the ionic equation showing the strong electrolytes completely dissociated into cations and anions. • Cancel the spectator ions on both sides of the ionic equation Q) Write the net ionic equation for the reaction of silver nitrate with sodium chloride. Dr. Ali Bumajdad

  22. precipitate Pb(NO3)2(aq) + 2NaI (aq)PbI2(s) + 2NaNO3(aq) Pb2+ + 2NO3- + 2Na+ + 2I-PbI2 (s) + 2Na+ + 2NO3- Pb2+ + 2I- PbI2 (s) PbI2 molecular equation ionic equation net ionic equation Na+ and NO3- are spectator ions Dr. Ali Bumajdad

  23. 2KNO3 (aq) + BaCl2 (aq) Ba(NO3)2 (aq) + 2KCl (aq) Na2SO4 (aq) + Pb(NO3)2 (aq) 2NaNO3 (aq) + PbSO4 (s) 3KOH (aq) + Fe(NO3)3 (aq) 3KNO3 (aq) + Fe(OH)3 (s) Sa. Ex. 4.8: what happen when the following pairs mixed: a) KNO3 and BaCl2 No net ionic eqn. No reaction b) Na2SO4 and Pb(NO3)2 reaction c) KOH and Fe(NO3)3 reaction Dr. Ali Bumajdad

  24. Sa. Ex. 4.9: Write the molecular, complete ionic and net ionic equations for the following mixed chemicals: 1) Potassium Chloride added to silver nitrate 2) Potassium hydroxide added to iron (III) nitrate Dr. Ali Bumajdad

  25. Q) Write the molecular, complete ionic and net ionic equations for the following mixed chemicals: • K2CrO4 and Ba(NO3)2 • HCl and NaOH • HC2H3O2 and KOH Dr. Ali Bumajdad

  26. 2Mg (s) + O2 (g) 2MgO (s) 2Mg 2Mg2+ + 4e- Oxidation-Reduction Reactions Redox Reactions (electron transfer reactions) • Oxidation: Loss of electrons Oxidation half-reaction (lose e-) Cation neutral We can say : Oxidation of MgorMg is oxidized We can say : Mgis a reducing agent

  27. We can say : reduction of O2or O2 is reduced We can say : O2is oxidation agent O2 + 4e- 2O2- 2Mg + O2 + 4e- 2Mg2+ + 2O2- + 4e- 2Mg + O2 2MgO • Reduction:Gain of electrons Reduction half-reaction (gain e-) neutral anion • Redox reaction: Gaining and losing of electrons Dr. Ali Bumajdad

  28. Oxidizing agent: Reactant reduced • Oxidizing agent: Reactant that gain electrons • Reducing agent: Reactant oxidized • Reducing agent: Reactant that lost electrons Dr. Ali Bumajdad

  29. Oxidation number The charge the atom would have in a molecule (or an ionic compound) if electrons were completely transferred. 1. O.N. of free elements is zero. Na, Be, K, Pb, H2, O2, P4 = 0 2. O.N. ofmonatomic ions = the charge on the ion. Li+, Li = +1; Fe3+, Fe = +3; O2-, O = -2 3. The sum of O.N. in a molecule isZero H2O = 2(+1) +(-2) =0 4.The sum of O.N. in a polyatomic ion = the charge on ion. SO4-2 = (X) +4(-2) =-2 5. Group IA metals = +1, IIA metals= +2 Dr. Ali Bumajdad

  30. 6.FO.N.= -1. 7.HO.N.= +1, except with metals in binary compounds = –1. 8.OO.N.= -2, except in H2O2 and O22- = –1. 9. When encounter conflict in rules6, 7, 8 the higher one take precedence. Dr. Ali Bumajdad

  31. Figure 4.10 The oxidation numbers of elements in their compounds

  32. Cu (s) + 2AgNO3 (aq) Cu(NO3)2 (aq) + 2Ag (s) Zn (s) + CuSO4 (aq) ZnSO4 (aq) + Cu (s) Cu2+ + 2e- Cu Cu Cu2+ + 2e- Zn Zn2+ + 2e- Ag+ + 1e- Ag Q) Zinc reacts with copper sulfate to form copper metal. What is the reducing agent in the reaction? Zn is the reducing agent Zn is oxidized Cu2+is reduced Cu2+ is the oxidizing agent Q) Copper wire reacts with silver nitrate to form silver metal. What is the oxidizing agent in the reaction? Cuis oxidized Cu is the reducing agent Ag+is reduced Ag+ is the oxidizing agent Dr. Ali Bumajdad

  33. Q) What are the oxidation numbers of all the elements in the following ? IF7 F = -1 HCO3- O = -2 H = +1 7x(-1) + I (?) = 0 3x(-2) + 1 + ? = -1 I = +7 C = +4 K2Cr2O7 NaIO3 O = -2 K = +1 O = -2 Na = +1 7x(-2) + 2x(+1) + 2x(Cr(?) = 0 3x(-2) + 1 + ? = 0 I = +5 Cr = +6

  34. Sa. Ex. 4.16: Assign oxidation states of all the atoms in: • CO2 • SF6 • NO3- Dr. Ali Bumajdad

  35. Q) Assign oxidation states of all the atoms in: • FeCl3 • b) KNO3 • c) H2O2 • d) Fe2(SO4)3 • e) Cr2O7 • f) ClO3- • g) Na2S4O6

  36. A + B C S + O2 SO2 C A + B 2KClO3 2KCl + 3O2 Types of Oxidation-Reduction Reactions Combination Reaction +4 -2 0 0 Decomposition Reaction +1 +5 -2 +1 -1 0

  37. A + BC AC + B Sr + 2H2O Sr(OH)2 + H2 TiCl4 + 2Mg Ti + 2MgCl2 Cl2 + 2KBr 2KCl + Br2 Types of Oxidation-Reduction Reactions Displacement Reaction +1 +2 0 0 Hydrogen Displacement +4 0 0 +2 Metal Displacement -1 0 0 -1 Halogen Displacement Dr. Ali Bumajdad

  38. M + BC AC + B Ca + 2H2O Ca(OH)2 + H2 Pb + 2H2O Pb(OH)2 + H2 The Activity Series for Metals Hydrogen Displacement Reaction M is metal BC is acid or H2O B is H2 Dr. Ali Bumajdad

  39. Cl2 + 2OH- ClO- + Cl- + H2O Chlorine Chemistry Types of Oxidation-Reduction Reactions Disproportionation Reaction Element is simultaneously oxidized and reduced. +1 -1 0 Dr. Ali Bumajdad

  40. Ca2+ + CO32- CaCO3 NH3 + H+ NH4+ Zn + 2HCl ZnCl2 + H2 Ca + F2 CaF2 Q) Classify the following reactions. Precipitation, Combination Acid-Base, Combination Redox (H2 Displacement) Redox, Combination Dr. Ali Bumajdad

  41. 3CH3CH2OH + 2K2Cr2O7 + 8H2SO4 Orange/ yellow 3CH3COOH + 2Cr2(SO4)3 + 2K2SO4 + 11H2O green Chemistry in Action: Breath Analyzer +6 +3 Dr. Ali Bumajdad

  42. Sa. Ex. 4.17: 2Al(s) + 3 I2(s) 2AlI3(s) • Identify the atoms that are oxidized, reduced and specify the oxidation and reducing agent. Dr. Ali Bumajdad

  43. Q) 14HCl + K2Cr2O7 2KCl + 2CrCl3 + 3Cl2 + 7H2O Identify the atoms that are oxidized, reduced and specify the oxidation and reducing agent. Dr. Ali Bumajdad

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