1. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Chemistry FIFTH EDITION by Steven S. Zumdahl University of Illinois

2. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 2 Chemistry FIFTH EDITION Chapter 4 Types of Chemical Reactions and Solution Stoichiometry Don’t forget Homework!!!!

3. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 3 What is one of the most important Substances on earth???????????? Water!!!!!!!!!!!!!!!!!!!!! What is one of its most valuable properties? Its ability to dissolve many different substances!!

4. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 4 Section 4.1 Water, The Common Solvent Aqueous Solutions Water is the dissolving medium, or solvent.

5. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 5 Figure 4.1 The Water Molecule is · Polar ·Bent

6. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 6 Some Properties of Water 4 Water is “bent” or V-shaped. 4 The O-H bonds are covalent. 4 Water is a polar molecule. Electrons are not equally shared. Unequal charge distribution. O—H δ - δ + 4 Hydration occurs when salts dissolve in water. Polarity gives water ability to dissolve cpds.

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 Hydration 4 Hydration occurs when salts dissolve in water. Attraction of positive ions for the negative ions is WEAKENED and replaced by strong water/ion interactions. When salts dissolve, positive and negative ions move around independently. They are hydrated by an unspecified number of water molecules.

9. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 9 Solubility Solubility of ionic substances in water varies greatly. It depends on the forces holding the solid together RELATIVE to the attractions of those ions for water molecules.

10. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 10 Water also dissolves NON-IONIC substances. Example: Ethanol CH 3 CH 2 OH

11. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 11 Figure 4.3 Polar Bond Ethanol contains polar O—H bond like water that makes it Very compatible with water.

12. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 12 Water doesn’t dissolve everything!! Example: Animal fat (Non-polar) General Rule: LIKE DISSOLVES LIKE

13. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 13 Section 4.2 The Nature of Aqueous Solutions: Strong & Weak Electrolytes

14. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 14 SOLUTION HOMOGENEOUS MIXTURE Solvent – Dissolving medium Solute – Substance dissolved

15. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 15 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)

16. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 16 A Solvent 4 retains its phase (if different from the solute) 4 is present in greater amount (if the same phase as the solute)

17. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 17 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

18. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 18 STRONG ELECTROLYTES Completely ionize or dissociate when dissolved in water Examples: Soluble salts Strong Acids Strong Bases

19. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 19 Figure 4.5 BaCl 2 Dissolving

20. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 20 Acids First studied by Arrenhius while studying conductivity of sol’ns. Found HCl, HNO 3, and H 2 SO 4 behaved as strong electrolytes. First defined acid as a substance that produced H + ions (protons) when dissolved in water.

21. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 21 Svante Arrhenius

22. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 22 Acids Strong acids -virtually every molecule ionizes to produce H + (H 3 O + ) in solution (Strong Electrolytes) hydrochloric acid i.e., HCl  H + (aq) + Cl - (aq)

23. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 23

24. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 24 http://www.mhhe.com/physsci/chemistry/essen tialchemistry/flash/acid13.swfhttp://www.mhhe.com/physsci/chemistry/essen tialchemistry/flash/acid13.swf

25. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 25 Figure 4.6 HCl (aq) is Completely Ionized

26. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 26 ionizes

27. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 27 Recall H 2 SO 4 can produce 2 H + ions. However, only the 1 st H + is completely ionized.

28. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 28 STRONG ACIDS: Virtually every molecules ionizes! HClO 4 (aq) H 2 SO 4 (aq) HNO 3 (aq) HCl (aq) HBr (aq) HI (aq) MEMORIZE!!!

29. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 29 Bases Strong bases - react completely with water to give OH  ions. - also strong electrolytes. sodium hydroxide NaOH (s)  Na + (aq) + OH - (aq)

30. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 30 Figure 4.7 An Aqueous Solution of Sodium Hydroxide

31. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 31 WEAK ELECTROLYTES Less than 100% dissociation or ionization. Very few ions formed. Most common are weak acids and weak bases.

32. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 32 Weak Acids Weak acids - ionize to a slight extent to give H + in solution acetic acid: CH 3 COOH formic acid: HCOOH

33. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 33 Figure 4.8 Acetic Acid in Water For every 100 molecules, only one ionizes. 99 remain intact! HC 2 H 3 O 2 Or CH 3 COOH Only one acidic Hydrogen!

34. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 34 http://www.mhhe.com/physsci/chemistry/essen tialchemistry/flash/acid13.swfhttp://www.mhhe.com/physsci/chemistry/essen tialchemistry/flash/acid13.swf

35. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 35 Weak Bases Weak bases - react only slightly with water to give OH  ions. Ammonia NH 3 (aq) + H 2 O (l)  NH 4 + (aq) + OH - (aq)

36. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 36 Figure 4.9 The Reaction of NH 3 in Water For every 100 molecules, only one ionizes. 99 remain intact!

37. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 37 Non-Electrolytes Substances that dissolve in water, but do not produce any ions. Examples: Ethanol – CH 3 CH 2 OH Sucrose – C 12 H 22 O 11 Molecules remain intact in water.

38. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 38 Section 4.3 The Composition of Solutions Important to know the Amount of Chemicals present in a Solution.

39. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 39 Molarity Molarity (M) = moles of solute per volume of solution in liters:

40. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 40 Recall 1.0 M NaCl means 1 mole of solid NaCl is dissolved in enough water to make 1.0 L of solution. The solution contains 1 mole of Na + ions and 1 mole of Cl - ions in 1.0 L of solution.

41. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 41 Standard Solution Solution whose concentration is accurately known.

42. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 42 Figure 4.10 Preparation of a Standard Solution

43. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 43 Dilution Solutions are often prepared by diluting more concentrated solutions.

44. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 44 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)

45. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 45 “Solutions by Dilution” Moles of solute after dilution EQUALS Moles of solute before dilution M 2 x V 2 = M 1 x V 1

46. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 46 Figure 4.11 (a) A Measuring Pipet(b) A Volumetric (transfer) Pipet

47. Copyright©2000 by Houghton Mifflin Company. All rights reserved. 47 Don’t forget your Homework!!