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Chapter 4

Chapter 4. Aqueous Reactions and Solution Stoichiometry. Properties of Aqueous Solutions. Solutions are homogeneous mixtures of 2 or more substances. Properties of Aqueous Solutions. Aqueous Solutions are solutions in which water is the dissolving medium. Properties of Aqueous Solutions.

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Chapter 4

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  1. Chapter 4 Aqueous Reactions and Solution Stoichiometry

  2. Properties of Aqueous Solutions • Solutions are homogeneous mixtures of 2 or more substances

  3. Properties of Aqueous Solutions • Aqueous Solutions are solutions in which water is the dissolving medium

  4. Properties of Aqueous Solutions • A solvent is the substance that is present in larger quantities.

  5. Properties of Aqueous Solutions • A solute is the substance being dissolved into the solvent.

  6. Properties of Aqueous Solutions • Electrolytes conduct electricity.

  7. Properties of Aqueous Solutions • Aqueous solutions made of ionic compounds are electrolytes due to the presence of ions.

  8. Properties of Aqueous Solutions • An aqueous solution of a molecular compound is called a nonelectrolyte

  9. Properties of Aqueous Solutions • Strong electrolytes exist in solution completely as ions (soluble ionic compounds)

  10. Properties of Aqueous Solutions • Weak electrolytes exist mostly as molecules

  11. Properties of Aqueous Solutions • Nonelectrolytes exist only as molecules

  12. Properties of Aqueous Solutions

  13. Precipitation Reactions • Precipitation reactions are those that result in the formation of an insoluble product

  14. Precipitation Reactions

  15. Precipitation Reactions • Precipitation reactions occur when certain pairs of oppositely charged ions attract to each other so strongly that they form an insoluble ionic solid

  16. Precipitation Reactions • Solubility of a substance is the amount of that substance that can be dissolved in a given quantity of solvent

  17. Precipitation Reactions • Any substance with a solubility less than 0.01mol/L will be referred to as insoluble

  18. Precipitation Reactions • The solubility guidelines for common ionic compounds in water is organized by anions

  19. Precipitation Reactions

  20. Practice 4.2 Soluble or Insoluble? • Sodium carbonate Lead (II) sulfate Barium nitrate Cobalt(II) hydroxide Ammonium phosphate

  21. Precipitation Reactions • To predict whether a precipitate will form when we mix aqueous solutions of electrolytes …

  22. Precipitation Reactions • (1)note the ions present in the reactants • (2) consider combinations of anions and cations • (3) use the table to predict if any of the combinations are insoluble

  23. Precipitation Reactions • Will a precipitate form when Mg(NO3)2 and NaOH are mixed?

  24. Precipitation Reactions • This is called a double replacement reaction. • AX + BY  AY + BX

  25. Practice 4.3 • (a) Write the balanced rxn and identify the ppt that forms when the following solutions are mixed: • (a) BaCl2 and K2SO4 • (b) Ba(NO3)2 and KOH • (c) Fe2(SO4)3 and LiOH

  26. Precipitation Reactions • A molecular equation shows the complete chemical formulas of the reactants and the products

  27. Precipitation Reactions • A complete ionic equation shows all strong electrolytes as ions rather than as compounds

  28. Precipitation Reactions • Spectator ions are ions that appear as identical forms on both sides of the equation; they are present but don’t play a direct role in the reaction

  29. Precipitation Reactions • Net ionic equations do not show spectator ions

  30. Writing Net Ionic Equations • Write a balanced mol. E.q • Rewrite to show ions that form in solution • Cancel spectator ions

  31. Practice 4.4 • Write the net ionic equation for the following rxns. (1) aqueous solutions of calcium chloride and sodium carbonate are mixed. (2) aqueous solutions of silver nitrate and potassium phosphate are mixed.

  32. Acid-Base Reactions • Acids produce H+ when dissolved in water • Acids are proton donors

  33. Acid-Base Reactions • Bases accept H+ions • Bases produce OH-when they dissolve in water

  34. Acid-Base Reactions • Strong acids and bases are strong electrolytes – ionize completely

  35. Acid-Base Reactions • Weak acids and bases are weak electrolytes – partially ionize ( do not write in ionized form)

  36. Acid-Base Reactions • List Strong Acids and Bases

  37. Practice Exercise 4.5 The following diagrams represent aqueous solutions of three acids (HX, HY, and HZ) with water molecules omitted for clarity. Rank them from strongest to weakest.

  38. Identifying Strong, Weak, and Non Electrolytes Chart

  39. Classifying SE, WE, or NE • 1. Is it ionic or molecular? • 2. If ionic – is it soluble? • 3. If molecular – is it an acid? • 4. If an acid – strong or weak? • 5. Is it weak base NH3? • 6. Everything else is a non electrolyte

  40. Practice 4.6 SE, WE, NE? CaCl2 HNO3 C2H5OH HCOOH KOH NH3

  41. Practice 4.6 Rank the following solution in order of least to most electrical conductivity. Ca(NO3)2 C6H12O6 CH3COONa or NaC2H3O2 CH3COOH or HC2H3O2

  42. Acid-Base Reactions • A neutralization reaction occurs when an acid and base are mixed producing water and salt • Salt means any ionic compound whose cation comes from the base and anion from the acid

  43. Acid-Base Reactions • Example: • Aq. solutions of hydrobromic acid and sodium hydroxide mix

  44. Acid-Base Reactions Aq. hydrochloric acid reacts with solid magnesium hydroxide.

  45. Acid-Base Reactions • Reactions with the S2- ion or CO32- ion with acids will form gases with low solubility in water

  46. Acid-Base Reactions Aq. HCl reacts with Baking soda

  47. Acid-Base Reactions Aq. Hydrochloric acid reacts with sodium sulfide

  48. Practice 4.7 Write a balanced molecular equation and net ionic equation for the following rxns: (a) aqueous solutions of acetic acid and barium hydroxide (b) aq solns of carbonic acid and potassium hydroxide

  49. Oxidation Numbers Oxidation numbers of an atom in a substance is a hypothetical charge based on a set of rules. 1. For an atom in its elemental form the oxidation number is always zero 2. For any monatomic ion the oxidation number equals the charge on the ion

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