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John E. McMurry Robert C. Fay

Lecture Presentation. Chapter 4 Reactions in Aqueous Solution. John E. McMurry Robert C. Fay. Solution Concentration: Molarity. Molarity : The number of moles of a substance dissolved in each liter of solution Solution : A homogeneous mixture Solute : The dissolved substance in a solution

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John E. McMurry Robert C. Fay

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  1. Lecture Presentation Chapter 4 Reactions in Aqueous Solution John E. McMurry Robert C. Fay

  2. Solution Concentration: Molarity Molarity: The number of moles of a substance dissolved in each liter of solution Solution: A homogeneous mixture Solute: The dissolved substance in a solution Solvent: The major component in a solution

  3. Solution Concentration: Molarity

  4. Balancing Chemical Equations Molarity converts between moles of solute and liters of solution: 1.00 mol of sodium chloride placed in enough water to make 1.00 L of solution would have a concentration equal to the following: Moles of solute Molarity = Volume of solution (L) 1.00 mol mol = 1.00 or 1.00 M 1.00 L L

  5. Solution Concentration: Molarity How many grams of solute would you use to prepare 1.50 L of 0.250 M glucose, C6H12O6? Molar mass C6H12O6 = 180.0 g/mol 0.250 mol × = 0.275 mol 1.50 L 1 L 180.0 g × = 49.5 g 0.275 mol 1 mol

  6. Diluting Concentrated Solutions Concentrated solution + Solvent Dilute solution Since the number of moles of solute remains constant, all that changes when adding more solvent is the volume of solution. initial final MiVi = MfVf

  7. Diluting Concentrated Solutions

  8. Diluting Concentrated Solutions Sulfuric acid is normally purchased at a concentration of 18.0 M. How would you prepare 250.0 mL of 0.500 M aqueous H2SO4? Add 6.94 mL 18.0 M sulfuric acid to enough water to make 250.0 mL of 0.500 M solution. Mi = 18.0 M Mf = 0.500 M Vi= ? mL Vf= 250.0 mL MfVf 0.500 M 250.0 mL Vi = = = 6.94 mL × Mi 18.0 M

  9. Electrolytes in Aqueous Solution Electrolytes: Substances that dissolve in water to produce conducting solutions of ions Nonelectrolytes: Substances that do not produce ions in aqueous solutions H2O NaCl(s) Na+(aq) + Cl¯(aq) H2O C12H22O11(s) C12H22O11(aq)

  10. Electrolytes in Aqueous Solution

  11. CH3CO2H(aq) H+(aq) + CH3CO2¯(aq) Electrolytes in Aqueous Solution Strong Electrolytes: Compounds that dissociate to a large extent into ions when dissolved in water Weak Electrolytes: Compounds that dissociate to a small extent into ions when dissolved in water KCl(aq) K+(aq) + Cl¯(aq)

  12. Electrolytes in Aqueous Solution StrongAcids: Hydrochloric acid, hydrobromic acid, hydroiodic acid, perchloric acid, nitric acid, sulfuric acid

  13. Electrolytes in Aqueous Solution Ionic compounds

  14. Electrolytes in Aqueous Solution Weak acids

  15. Electrolytes in Aqueous Solution Molecular compounds (other than any strong or weak electrolytes)

  16. Pb(NO3)2(aq) + 2KI(aq) 2KNO3(aq) + PbI2(s) Types of Chemical Reactions in Aqueous Solution Precipitation Reactions: Processes in which soluble reactants yield an insoluble solid product that falls out of solution

  17. Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g) Types of Chemical Reactions in Aqueous Solution Oxidation–Reduction (Redox) Reactions: Processes in which one or more electrons are transferred between reaction partners (atoms, molecules, or ions)

  18. HCl(aq) + NaOH(aq) H2O(l) + NaCl(aq) Types of Chemical Reactions in Aqueous Solution Acid-Base Neutralization Reactions: Processes in which an acid reacts with a base to yield water plus an ionic compound called a salt

  19. Pb(NO3)2(aq) + 2KI(aq) 2KNO3(aq) + PbI2(s) Aqueous Reactions and Net Ionic Equations Molecular Equation: All substances in the chemical equation are written using their complete formulas as if they were molecules. Strong electrolytes Precipitate

  20. Aqueous Reactions and Net Ionic Equations Ionic Equation: All of the strong electrolytes are written as ions. Pb(NO3)2(aq) 2KI(aq) Pb2+(aq) + 2NO3¯(aq) + 2K+(aq) + 2I¯ (aq) 2K+(aq) + 2NO3¯(aq) + PbI2(s) 2KNO3(aq)

  21. Aqueous Reactions and Net Ionic Equations Spectator Ions: Ions that undergo no change during the reaction and appear on both sides of the reaction arrow. Pb2+(aq) + 2NO3¯(aq) + 2K+(aq) + 2I¯(aq) 2K+(aq) + 2NO3¯(aq) + PbI2(s)

  22. Pb2+(aq) + 2I¯(aq) PbI2(s) Aqueous Reactions and Net Ionic Equations Net Ionic Equation: Only the ions undergoing change are shown.

  23. Precipitation Reactions and Solubility Guidelines • 1. A compound is probably soluble if it contains one of the following cations: • Group 1A cation: Li+, Na+, K+, Rb+, Cs+ • Ammonium ion: NH4+ • 2. A compound is probably soluble if it contains one of the following anions: • Halide: Cl¯, Br-, I¯ • Except Ag+, Hg22+, and Pb2+ compounds • NO3¯(nitrate), ClO4¯(perchlorate), CH3CO2¯(acetate), and SO42¯(sulfate) • ExceptSr2+, Ba2+, Hg22+, and Pb2+ sulfates

  24. Precipitation Reactions and Solubility Guidelines

  25. Precipitation Reactions and Solubility Guidelines Write the molecular, ionic, and net ionic equations for the reaction that occurs when aqueous solutions of AgNO3 and Na2CO3 are mixed.

  26. AB + CD CB + AD Precipitation Reactions and Solubility Guidelines Write the molecular, ionic, and net ionic equations for the reaction that occurs when aqueous solutions of AgNO3 and Na2CO3 are mixed. Write the chemical formulas of the products (use proper ionic rules). AgNO3(aq) + Na2CO3(aq) • Ag2CO3 + NaNO3 Double replacement reaction

  27. 2AgNO3(aq) + Na2CO3(aq) Ag2CO3(s) + 2NaNO3(aq) Precipitation Reactions and Solubility Guidelines Write the molecular, ionic, and net ionic equations for the reaction that occurs when aqueous solutions of AgNO3 and Na2CO3 are mixed. 2. Molecular Equation: Balance the equation and predict the solubility of each possible product. Neither the cation nor the anion is in the solubility list. Contains a group 1A cation

  28. Precipitation Reactions and Solubility Guidelines Write the molecular, ionic, and net ionic equations for the reaction that occurs when aqueous solutions of AgNO3 and Na2CO3 are mixed. 3. Ionic Equation: Dissociate the soluble ionic compounds. 2AgNO3(aq) Na2CO3(aq) 2Ag+(aq) + 2NO3¯(aq) + 2Na+(aq) + CO32¯ (aq) Ag2CO3(s) + 2Na+(aq) + 2NO3¯(aq) 2NaNO3(aq)

  29. 2Ag+(aq) + CO32¯(aq) Ag2CO3(s) Precipitation Reactions and Solubility Guidelines Write the molecular, ionic, and net ionic equations for the reaction that occurs when aqueous solutions of AgNO3 and Na2CO3 are mixed. 4. Net Ionic Equation: Eliminate the spectator ions from the ionic equation. 2Ag+(aq) + 2NO3–(aq) + 2Na+(aq) + CO32¯(aq) Ag2CO3(s) + 2Na+(aq) + 2NO3¯(aq)

  30. HCl(aq) + H2O(aq) HCl(aq) HA(aq) H3O+(aq) + Cl¯(aq) H+(aq) + A¯(aq) H+(aq) + Cl¯(aq) Acids, Bases, and Neutralization Reactions Acid (Arrhenius): A substance that dissociates in water to produce hydrogen ions, H+: In water, acids produce hydronium ions, H3O+:

  31. NH3(aq) + H2O(aq) NaOH(aq) MOH(aq) M+(aq) + OH¯(aq) Na+(aq) + OH¯(aq) NH4+(aq) + OH¯(aq) Acids, Bases, and Neutralization Reactions Base (Arrhenius): A substance that dissociates in water to produce hydroxide ions, OH¯: Ammonia is weakly basic because it reacts to a small extent with water to yield ammonium and hydroxide ions:

  32. Acids, Bases, and Neutralization Reactions Strong acids and strong bases are strong electrolytes. Weak acids and weak bases are weak electrolytes.

  33. Acids, Bases, and Neutralization Reactions Binary Acids HClhydrochloricacid HBrhydrobromicacid HF hydrofluoricacid

  34. -ous -ite -ic -ate Acids, Bases, and Neutralization Reactions

  35. HA(aq) + MOH(aq) MA(aq) + H2O(l) Acids, Bases, and Neutralization Reactions These acid–base neutralization reactions are double-replacement reactions just like the precipitation reactions: Acid Base Salt Water

  36. Acids, Bases, and Neutralization Reactions Write the molecular, ionic, and net ionic equations for the reaction of aqueous HBr and aqueous Ba(OH)2. Write the chemical formulas of the products (use proper ionic rules for the salt). HBr(aq) + Ba(OH)2(aq) H2O + BaBr2 Acid Base Water Salt

  37. 2HBr(aq) + Ba(OH)2(aq) 2H2O(l) + BaBr2(aq) Acids, Bases, and Neutralization Reactions Write the molecular, ionic, and net ionic equations for the reaction of aqueous HBr and aqueous Ba(OH)2. 2. Molecular Equation: Balance the equation and predict the solubility of the salt in the products. Use the solubility rules.

  38. Acids, Bases, and Neutralization Reactions Write the molecular, ionic, and net ionic equations for the reaction of aqueous HBr and aqueous Ba(OH)2. 3. Ionic Equation: Dissociate the strong acid and the soluble ionic compounds. 2HBr(aq) Ba(OH)2(aq) 2H+(aq) + 2Br¯(aq) + Ba2+(aq) + 2OH¯(aq) 2H2O(l) + Ba2+(aq) + 2Br¯(aq) BaBr2(aq)

  39. 2H+(aq) + 2OH¯(aq) H+(aq) + OH¯(aq) H2O(l) 2H2O(l) Acids, Bases, and Neutralization Reactions Write the molecular, ionic, and net ionic equations for the reaction of aqueous HBr and aqueous Ba(OH)2. 4. Net Ionic Equation: Eliminate the spectator ions from the ionic equation. 2H+(aq) + 2Br¯(aq) + Ba2+(aq) + 2OH¯(aq) 2H2O(l) + Ba2+(aq) + 2Br1¯(aq)

  40. Acids, Bases, and Neutralization Reactions Write the molecular, ionic, and net ionic equations for the reaction of aqueous NaOH and aqueous HF. Write the chemical formulas of the products (use proper ionic rules or the salt). HF(aq) + NaOH(aq) H2O + NaF Acid Base Water Salt

  41. HF(aq) + NaOH(aq) H2O(l) + NaF(aq) Acids, Bases, and Neutralization Reactions Write the molecular, ionic, and net ionic equations for the reaction of aqueous NaOH and aqueous HF. 2. Molecular Equation: Balance the equation and predict the solubility of the salt in the products. Use the solubility rules.

  42. Acids, Bases, and Neutralization Reactions Write the molecular, ionic, and net ionic equations for the reaction of aqueous NaOH and aqueous HF. 3. Ionic Equation: Dissociate the soluble ionic compounds. NaOH(aq) HF(aq) + Na+(aq) + OH¯(aq) H2O(l) + Na+(aq) + F¯(aq) NaF(aq)

  43. HF(aq) + OH¯(aq) H2O(l) + F¯(aq) Acids, Bases, and Neutralization Reactions Write the molecular, ionic, and net ionic equations for the reaction of aqueous NaOH and aqueous HF. 4. Net Ionic Equation: Eliminate the spectator ions from the ionic equation. HF(aq) + Na+(aq) + OH¯(aq) H2O(l) + Na+(aq) + F¯(aq)

  44. aA + bB cC + dD Solution Stoichiometry Volume of solution of A Moles of A Moles of B Volume of solution of B Molarity of A Mole ratio between A and B (coefficients) Molarity of B

  45. H2SO4(aq) + 2NaOH(aq) Na2SO4(aq) + 2H2O(l) Solution Stoichiometry What volume of 0.250 M H2SO4 is needed to react with 50.0 mL of 0.100 M NaOH? Volume of solution of H2SO4 Moles of H2SO4 Moles of NaOH Volume of solution of NaOH Molarity of H2SO4 Mole ratio between H2SO4 and NaOH Molarity of NaOH

  46. H2SO4(aq) + 2NaOH(aq) Na2SO4(aq) + 2H2O(l) Solution Stoichiometry Moles of NaOH available: 0.100 mol 1 L × × = 0.00500 mol NaOH 50.0 mL NaOH 1 L 1000 mL Volume of H2SO4 needed: 1 mol H2SO4 1 L solution 1000 mL 0.00500 molNaOH × × × 2 mol NaOH 0.250 mol H2SO4 1 L 10.0 mL solution (0.250 M H2SO4)

  47. HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l) Measuring the Concentration of a Solution: Titration Titration: A procedure for determining the concentration of a solution by allowing a measured volume of that solution to react with a second solution of another substance (the standard solution) whose concentration is known. Once the reaction is complete, you can calculate the concentration of the unknown solution. How can you tell when the reaction is complete?

  48. Measuring the Concentration of a Solution: Titration

  49. HCl(aq) + NaOH(aq) NaCl(aq) + 2H2O(l) Measuring the Concentration of a Solution: Titration 48.6 mL of a 0.100 M NaOH solution is needed to react with 20.0 mL of an unknown HCl concentration. What is the concentration of the HCl solution? Volume of solution of NaOH Moles of NaOH Moles of HCl Volume of solution of HCl Molarity of NaOH Mole ratio between NaOH and HCl Molarity of HCl

  50. HCl(aq) + NaOH(aq) NaCl(aq) + 2H2O(l) Measuring the Concentration of a Solution: Titration Moles of NaOH available: 0.100 mol 1 L 48.6 mL NaOH × × = 0.00486 mol NaOH 1 L 1000 mL Moles of HCl reacted: 1 mol HCl = 0.00486 mol HCl × 0.00486 molNaOH 1 mol NaOH Concentration of HCl solution: 0.00486 molHCl 1000 mL = 0.243 M HCl × 20.0 mL solution 1 L

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