1. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Reactions Chapter 4

2. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 2 Aqueous Solutions Water is the dissolving medium, or solvent.

3. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 3 Figure 4.1 The Water Molecule is Polar

4. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 4 Some Properties of Water 4 Water is “bent” or V-shaped. 4 The O-H bonds are covalent. 4 Water is a polar molecule. 4 Hydration occurs when salts dissolve in water.

5. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 5

6. 6 http://mathinscience.info/teach/k5_science/c hemistry/mastering_matter/matter_animatio ns/salt_cystl_watr_mol_web.swfhttp://mathinscience.info/teach/k5_science/c hemistry/mastering_matter/matter_animatio ns/salt_cystl_watr_mol_web.swf

7. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 7 Figure 4.2 Polar Water Molecules Interact with the Positive and Negative Ions of a Salt

8. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 8 Figure 4.3 Polar Bond

9. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 9 A Solute 4 dissolves in water (or other “solvent”) 4 changes phase (if different from the solvent) 4 is present in lesser amount (if the same phase as the solvent)

10. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 10 A Solvent 4 retains its phase (if different from the solute) 4 is present in greater amount (if the same phase as the solute)

11. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 11 Electrolytes Strong - conduct current efficiently NaCl, HNO 3 Weak - conduct only a small current vinegar, tap water Non - no current flows pure water, sugar solution

12. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 12 Figure 4.5 BaCI 2 Dissolving

13. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 13 Acids Strong acids -dissociate completely to produce H + in solution hydrochloric and sulfuric acid Weak acids - dissociate to a slight extent to give H + in solution acetic and formic acid

14. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 14 Figure 4.6 HCI (aq) is Complete ly Ionized

15. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 15 Figur e 4.8 Acetic Acid in Water

16. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 16 Bases Strong bases - react completely with water to give OH  ions. sodium hydroxide Weak bases - react only slightly with water to give OH  ions. ammonia

17. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 17 Molarity Molarity (M) = moles of solute per volume of solution in liters:

18. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 18 Common Terms of Solution Concentration Stock - routinely used solutions prepared in concentrated form. Concentrated - relatively large ratio of solute to solvent. (5.0 M NaCl) Dilute - relatively small ratio of solute to solvent. (0.01 M NaCl)

19. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 19 Figure 4.10 Preparation of a Standard Solution

20. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 20 Types of Double Displacement Reactions 4 Precipitation reactions AgNO 3 (aq) + NaCl(aq)  AgCl(s) + NaNO 3 (aq) 4 Acid-base reactions NaOH(aq) + HCl(aq)  NaCl(aq) + H 2 O(l) 4 Oxidation-reduction reactions Fe 2 O 3 (s) + Al(s)  Fe(l) + Al 2 O 3 (s)

21. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 21 Simple Rules for Solubility 1.Most nitrate (NO 3  ) salts are soluble. 2.Most alkali (group 1A) salts and NH 4 + are soluble. 3.Most Cl , Br , and I  salts are soluble (NOT Ag +, Pb 2+, Hg 2 2+ ) 4.Most sulfate salts are soluble (NOT BaSO 4, PbSO 4, HgSO 4, CaSO 4 ) 5.Most OH  salts are only slightly soluble (NaOH, KOH are soluble, Ba(OH) 2, Ca(OH) 2 are marginally soluble) 6.Most S 2 , CO 3 2 , CrO 4 2 , PO 4 3  salts are only slightly soluble.

22. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 22 Describing Reactions in Solution 1.Molecular equation (reactants and products as compounds) AgNO 3 (aq) + NaCl(aq)  AgCl(s) + NaNO 3 (aq) 2.Complete ionic equation (all strong electrolytes shown as ions) Ag + (aq) + NO 3  (aq) + Na + (aq) + Cl  (aq)  AgCl(s) + Na + (aq) + NO 3  (aq)

23. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 23 Describing Reactions in Solution (continued) 3.Net ionic equation (show only components that actually react) Ag + (aq) + Cl  (aq)  AgCl(s) Na + and NO 3  are spectator ions.

24. Quick Review – Are you Ready? Copyright©2000 by Houghton Mifflin Company. All rights reserved. 24 1.Yes 2.No

25. When Fe(NO 3 ) 2 dissolves in water, what particles are present in the solution? 1.Fe + and (NO 3 ) 2 – 2.Fe 2+ and 2 NO 3 – 3.Fe and 2 NO 3 4.Fe and N 2 and 3 O 2

26. Pb(NO 3 ) 2 + 2 KI  PbI 2 + 2 KNO 3 What is the observable evidence that the above reaction occurs? 1.An explosion. 2.A gas forms. 3.The solution boils. 4.A solid forms.

27. When an acid and a base react to form a salt and water, the reaction is called a(n): 1.cancellation. 2.elimination. 3.neutralization. 4.adduct formation.

28. Which mixture will produce a precipitate? Copyright©2000 by Houghton Mifflin Company. All rights reserved. 28 1. NH 3 + HF 2. HClO 4 + KOH 3. Na 2 SO 4 + PbCl 2 4. Ca(NO 3 ) 2 + KC 2 H 3 O 2 5. (NH 4 ) 2 CO 3 + Na 3 PO 4 1. 2.2 3.3 4.4 5.5

29. What is(are) the spectator ion(s) in the following reaction? KOH (aq) + HF (aq) KF (aq) + H 2 O (l) 1.K + 2.F – 3.K + and F – 4.OH – and H + 5.OH –

30. Which of the following reactions has the net ionic equation: H + (aq) + OH – (aq) H 2 O (l) 1.Reaction 1 2.Reactions 1, 4 3.Reactions 2, 3 4.Reactions 2, 4 5.Reactions 3, 4

31. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 31

32. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 32 Other Reactions Single displacement Combustion Synthesis Decomposition All of these involve a transfer of electrons and are oxidation-reduction (Redox) reactions

33. © 2009, Prentice- Hall, Inc. Oxidation-Reduction Reactions An oxidation occurs when an atom or ion loses electrons. A reduction occurs when an atom or ion gains electrons. One cannot occur without the other.

34. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 34 Rules for Assigning Oxidation States 1. Oxidation state of an atom in an element = 0 2. Oxidation state of monatomic ion = charge 3. Oxygen =  2 in covalent compounds (except in peroxides where it =  1) 4. H = +1 when bonded to nonmetal; -1 when bonded to metal

35. 5. Fluorine =  1 in compounds The other halogens have an oxidation number of −1 when they are negative; they can have positive oxidation numbers, however, most notably in oxyanions (polyatomic ions with oxygen) 6. Sum of oxidation states = 0 in compounds Sum of oxidation states = charge of the ion Copyright©2000 by Houghton Mifflin Company. All rights reserved. 35

36. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 36 Redox Reactions - Terms Oxidation – loss of electrons (increase in oxidation number) Reduction – gain of electrons (decrease in oxidation number) Oxidizing agent – the compound that is the electron acceptor Reducing agent – the compound that is the electron donor

37. When an atom undergoes reduction, it _______ electrons. 1.gains 2.loses 3.retains 4.balances

38. What is the oxidation number of sulfur in the following compound? SO 2 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 38 1.-4 2.+4 3.-2 4.+2

39. What is the oxidation number of oxygen in the following compound? MgO Copyright©2000 by Houghton Mifflin Company. All rights reserved. 39 1.-4 2.+4 3.-2 4.+2

40. What is the oxidation number of Manganese in the following compound? MnO 2 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 40 1.-4 2.+4 3.-2 4.+2

41. What is the oxidation number of Fluorine in the following compound? F 2 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 41 1.-1 2.+1 3.0 4.-2

42. What is the oxidation number of Sulfur in the following compound? SO 4 2- Copyright©2000 by Houghton Mifflin Company. All rights reserved. 42 1.+8 2.+6 3.-2 4.+4

43. What is the oxidation number of manganese in the permanganate ion? Copyright©2000 by Houghton Mifflin Company. All rights reserved. 43 1.+8 2.+6 3.-6 4.+7

44. What is the oxidation number of nitrogen in the nitrite ion? Copyright©2000 by Houghton Mifflin Company. All rights reserved. 44 1.+3 2.+5 3.-5 4.+2

45. What is reduced in the following equation? Al + Cu(NO 3 ) 2  Cu + Al(NO 3 ) 3 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 45 1.Al 2.Cu 3.Cu(NO 3 ) 2 4.Al(NO 3 ) 3

46. What is oxidized in the following equation? Al + Cu(NO 3 ) 2  Cu + Al(NO 3 ) 3 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 46 1.Al 2.Cu 3.Cu(NO 3 ) 2 4.Al(NO 3 ) 3

47. What is reducing agent in the following equation? Al + Cu(NO 3 ) 2  Cu + Al(NO 3 ) 3 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 47 1.Al 2.Cu 3.Cu(NO 3 ) 2 4.Al(NO 3 ) 3

48. What is oxidizing agent in the following equation? Al + Cu(NO 3 ) 2  Cu + Al(NO 3 ) 3 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 48 1.Al 2.Cu 3.Cu(NO 3 ) 2 4.Al(NO 3 ) 3

49. Which substance is serving as the reducing agent in the following reaction? 14H + + Cr 2 O 7 2- + 3Ni  3Ni 2+ + 2Cr 3+ + 7H 2 O Copyright©2000 by Houghton Mifflin Company. All rights reserved. 49 A.H 2 O B.H + C.Ni 2+ D.Ni E.Cr 2 O 7 2-

50. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 50 Balancing by Half-Reaction Method 1.Write separate reduction, oxidation reactions. 2.For each half-reaction:  Balance elements (except H, O)  Balance O using H 2 O  Balance H using H +  Balance charge using electrons

51. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 51 Balancing by Half-Reaction Method (continued) 3.If necessary, multiply by integer to equalize electron count. 4.Add half-reactions. 5.Check that elements and charges are balanced.

52. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 52 Half-Reaction Method - Balancing in Base 1.Balance as in acid. 2.Add OH  that equals H + ions (both sides!) 3.Form water by combining H +, OH . 4.Check elements and charges for balance.

53. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 53 Performing Calculations for Acid-Base Reactions 1.List initial species and predict reaction. 2.Write balanced net ionic reaction. 3.Calculate moles of reactants. 4.Determine limiting reactant. 5.Calculate moles of required reactant/product. 6.Convert to grams or volume, as required.

54. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 54 Key Titration Terms Titrant - solution of known concentration used in titration Analyte - substance being analyzed Equivalence point - enough titrant added to react exactly with the analyte Endpoint - the indicator changes color so you can tell the equivalence point has been reached.