1. Chemical Reactions Reactions in Aqueous Solutions

2. Learning Goals • Write complete ionic and net ionic equations for chemical reactions in aqueous solutions. • Predict whether reactions in aqueous solutions will produce a precipitate, water, or a gas. • Identify acid-base reactions and oxidation-reduction reactions.

3. Aqueous Solutions • An aqueous solutioncontains one or more dissolved substances (called solutes) in water (the solvent).

4. Aqueous Solutions • Water is always the solvent in an aqueous solution. • Solutes can be anything that is dissolved in water: • Ex: Sugar, alcohol, acids, bases, ionic compounds

5. Aqueous Solutions • When ionic compounds dissolve in water, their ions separate in a process called dissociation.

7. Aqueous Solutions • When two solutions that contain ions as solutes are combined, the ions might react. • If they react, it is always a double replacement reaction. • 3 types of products can form, a precipitate, water, or gas.

8. Precipitation Reactions • Precipitation Reactions

12. Solubility Rules • Use the solubility rules to predict which of the following substances are likely to be soluble in water: • Aluminum nitrate • Magnesium chloride • Rubidium sulfate • Nickel (II) hydroxide • Lead (II) sulfide • Magnesium hydroxide • Iron (III) phosphate

13. Practice • Use the solubility rules to predict what will happen when the following solutions are mixed. Write the balanced equation for any reaction that occurs. • KNO3 (aq) and BaCl2(aq)

14. Practice • Na2SO4(aq) and Pb(NO3)2(aq) • KOH(aq) and Fe(NO3) 3(aq)

15. Practice • Ba(NO3)2 (aq) and NaCl(aq) • Na2S (aq) and Cu(NO3)2(aq)

16. Practice • NH4Cl(aq) and Pb(NO3)2(aq)

17. Ionic Equations • 2NaOH(aq) + CuCl2(aq) → 2NaCl(aq) + Cu(OH)2(s) • 2Na+(aq) + 2OH–(aq) + Cu2+ (aq)+ 2Cl–(aq) → 2Na+(aq) + 2Cl–(aq) + Cu(OH)2(s)

18. Ionic Equations • Ionic equations that show all of the particles in a solution as they actually exist are called complete ionic equations.

19. Ionic Equations • Ions that do not participate in a reaction are called spectator ionsand are not usually written in ionic equations.

20. Ionic Equations • Formulas that include only the particles that participate in reactions are called net ionic equations.

21. Ionic Equations • 2NaOH(aq) + CuCl2(aq) → 2NaCl(aq) + Cu(OH)2(s) • 2Na+(aq) + 2OH–(aq) + Cu2+ (aq)+ 2Cl–(aq) → 2Na+(aq) + 2Cl–(aq) + Cu(OH)2(s) • 2OH–(aq) + Cu2+(aq) → Cu(OH)2(s)

22. Practice • Write chemical, complete ionic, and net ionic equations for each of the following reactions that produce a precipitate. • Aqueous solutions of potassium iodide and silver nitrate are mixed, forming the precipitate silver iodide.

23. Practice • Aqueous solutions of aluminum chloride and sodium hydroxide are mixed, forming the precipitate aluminum hydroxide.

24. Practice • When aqueous solutions of sodium carbonate and manganese (V) chloride are mixed, a precipitate containing manganese is formed.

25. Reactions that Produce Water • Some reactions produce more water molecules. • No evidence of a chemical reaction is observable. • Water is a very stable compound. • When substances that can form water are mixed, there is a strong tendency for the reaction to occur.

26. Reactions that Produce Water • Acids and Bases: • Arrhenius acids: substances that produces H+ ions when dissolved in water. • Acids that completely ionize into H+ are called strong acids.

27. Reactions that Produce Water • Acids and Bases: • Arrhenius bases: substances that produces OH- ions when dissolved in water. • Bases that completely ionize into OH- are called strong bases.

28. Reactions that Produce Water • HBr(aq) + NaOH(aq) → H2O(l) + NaBr(aq) • Without spectator ions H+(aq) + OH–(aq) → H2O(l).

30. Practice • Write chemical, complete ionic, and net ionic equations for each of the following reactions that produce water. • Mixing sulfuric acid and aqueous potassium hydroxide produces water and aqueous potassium sulfate.

31. Practice • When benzoic acid (HC7H5O2) and magnesium hydroxide are mixed, water and magnesium benzoate are produced.

32. Practice • Aqueous nitric acid reacts with aqueous potassium hydroxide.

33. Reactions that Produce Gas • Gases that are commonly produced are carbon dioxide, hydrogen cyanide, and hydrogen sulfide. • 2HI(aq) + Li2S(aq) → H2S(g) + 2LiI(aq)

35. Reactions that Produce Gas • Two reactions can be combined and represented by a single chemical reaction.

36. Reactions that Produce Gas • Combined equation • HCl(aq) + NaHCO3(aq) + H2CO3(aq) → H2CO3(aq) + NaCl(aq) + H2O(l) + CO2(g) • Overall equation • HCl(aq) + NaHCO3(aq) → H2O(l) + CO2(g) + NaCl(aq)

37. Practice • Write chemical, complete ionic, and net ionic equations for each of the following reactions. • Perchloric acid reacts with aqueous potassium carbonate, forming carbon dioxide gas and water.

38. Practice • Nitric acid reacts with aqueous potassium rubidium sulfide (KBrS), forming hydrogen sulfide gas.

39. Oxidation-Reduction Reactions • Oxidation-Reduction Reactions involve a transfer of electrons. • Often reactions between metals and nonmetals.

40. Oxidation-Reduction Reactions • 2Na(s) + Cl2(g)  2NaCl(s) • Na + Cl  Na+ + Cl- e-

41. Oxidation-Reduction Reactions • 2Mg(s) + O2(g)  2MgO(s) • Mg + O  Mg2+ + O2- e- e- Also a combustion reaction!!

42. Oxidation-Reduction Reactions • All combustion reactions are oxidation-reduction reactions!

43. Oxidation-Reduction Reactions • 2Al(s) + Fe2O3(s)  2Fe(s) + Al2O3(s) • Al + Fe3+  Fe + Al3+ e- e- e- Also a single replacement reaction!!

44. Oxidation-Reduction Reactions • Oxidation-Reduction Reactions

45. Practice • For each reaction, show how electrons are gained and lost: • 2Na(s) + Br2(l)  2NaBr (s)

46. Practice • For each reaction, show how electrons are gained and lost: • 2Ca(s) + O2(g)  2CaO(s)

47. Classifying Reactions • Synthesis (combination) • Combustion • Decomposition • Single Replacement

48. Classifying Reactions • Double Replacement • Precipitation Reactions • Acid-Base Reactions • Oxidation-Reduction Reactions

49. Classifying Reactions • Classify each of the following reactions in as many ways possible. • 2K(s) + Cl2(g)  2KCl(s) • 2Mg(s) + O2(g)  2MgO(s)

50. Classifying Reactions • Classify each of the following reactions in as many ways possible. • Fe2O3(s) + 2Al(s)  Al2O3(s) + 2Fe(s) • HNO3(aq) + NaOH(aq) → H2O(l) + NaNO3 (aq)