1. Chapter 8 Reactions in Aqueous Solution

2. Will a reaction Occur? Driving Forces in a Chemical Reaction  Formation of a solid  Formation of water  Formation of a gas  Transfer of electrons

3. Types of Reactions Double Replacement Reactions 1. Precipitation Reactions 2. Acid and Base Reactions Red-ox Reactions 3. Single Replacement Reactions 4. Synthesis Reactions 5. Decomposition Reactions 6. Combustion Reactions

4. Double Replacement Reactions 1 – Precipitation Reactions 2 – Acid and Base Reactions

5. Double Replacement Reactions – Reactions involving two compounds in which two elements switch places General Form: AB + CD → AD + CB Double Replacement

6. Solid Formation: Precipitation Reactions (#1) Precipitation Reaction – a reaction that produces a precipitate K 2 CrO 4 (aq) + Ba(NO 3 ) 2 (aq) → BaCrO 4 (s) + 2 KNO 3 (aq) In order to know what will form, you need to know what is in solution!

7. Solid Formation In solution, most compounds break down into their ions Ba(NO 3 ) 2 (aq) → Ba 2+ (aq) + 2 NO 3 1- (aq) Strong Electrolyte – completely dissociates into ions in solution (dissolving.mov)dissolving.mov The reaction is best demonstrated by: 2 K 1+ (aq) + CrO 4 2- (aq) + Ba 2+ (aq) + 2 (NO 3 ) 1- (aq) → BaCrO 4 (s) + 2 K 1+ (aq) + 2 NO 3 1- (aq)

8. Solid Formation - Solubility Rules Soluble solid – a solid that dissolves in water Insoluble solid – a solid that does not dissolve in water Slightly soluble solid – a small amount of the solid dissolves in water

9. Solid Formation - Solubility Rules Soluble –  NO 3 - salts  Na+, K+, NH 4 + salts  Cl-, Br-, I- salts, but not when with Ag+, Hg 2 2+, and Pb 2+  SO 4 2- salts, but not when with Ba 2+, Pb 2+, and Ca 2+

10. Solid Formation - Solubility Rules Insoluble  S 2-  CO 3 2-  PO 4 3-  OH-, but not when with Na +, K +, Ca 2+

11. Visualizing Solubility

12. Describing reactions in Aqueous Solutions Molecular Equation – Represents all molecules involved in a reaction Complete Ionic Equation – represents all of the ions in the reacting solution Net Ionic Equation – shows only the ions directly involved in the reaction, spectator ions are not included Spectator Ions – ions that are listed in the complete ionic equation, but not in the net ionic equation. They are not involved in the reaction.

13. Describing reactions in Aqueous Solutions Molecular Equation Pb(NO 3 ) 2 (aq) + Na 2 SO 4 (aq) → PbSO 4 (s) + 2NaNO 3 (aq) Net Ionic Equation Pb 2+ (aq) + SO 4 2- (aq) → PbSO 4 (s) Complete Ionic Equation Pb 2+ (aq) + 2(NO 3 ) - (aq) + 2Na 1+ (aq) + SO 4 2- (aq) → PbSO 4 (s) + 2Na + (aq) + 2NO 3 - (aq)

14. Describing reactions in Aqueous Solutions Write the balanced molecular, ionic, and net ionic equations:  Aqueous sodium chloride is added to aqueous silver nitrate to form solid silver chloride plus sodium nitrate

15. Formation of Water: (#2) Acids & Bases Acid – “acidus” or sour – a substance that produces H+ ions (protons) when it is dissolved in water  Strong acid – completely dissociates in water  HCl(aq) → H 1+ (aq) + Cl 1- (aq)

16. Base – “alkalis” slippery in feel and sour in taste – a substance that produces hydroxide (OH) ions in solution  Strong base – completely dissociates in water  NaOH(aq) → Na 1+ (aq) + OH 1- (aq) Formation of Water: (#2) Acids & Bases

17. Formation of Water: Acids & Bases When acids and bases react, they neutralize each other Neutralization – When a strong acid and strong base react to form water and an aqueous salt

19. Acids & Bases Write the molecular, Complete ionic, and net ionic equation for the reaction of nitric acid and potassium hydroxide

20. Arrhenius Model  Acids – anything that produces H1+  Bases – anything that produces OH1-  Strong – Completely dissociates Bronsted-Lowrey  Acids – Proton Donor  Bases – Proton Acceptor  Weak – Slightly Soluble, slight dissociation Acids & Bases

21. Acid + Base → Conjugate Acid + Conjugate Base H 2 SO 4 + NaOH → H 2 O + Na 2 SO 4 To find the conjugate acid – follow the hydrogen To find the conjugate base - follow the anion from the acid Acids & Bases

22. Concentration – How much material is dissolved in your solution  Concentrated – much material is dissolved  Dilute – little material is dissolved Molarity – Unit of Concentration in Chemistry  The number of MOLES of material per LITER of solution  Unit = M  M = moles / L  Example: 8M HCl = an 8 Molar solution of Hydrochloric Acid, 8 moles of HCl are dissolved in every liter of the solution Acids & Bases

23. Titration – measuring the exact amount of an acid that reacts with an exact amount of a base.  If you know the concentration of one of the solutions, it can be used to calculate the concentration of the other Equivalence point – the point of neutralization, the amount of acid and base are equal in solution Standard Solutions – solutions of known concentration Acids & Bases

24. Burette – the tool used to dispense an exact amount of a standard solution in a titration Indicators – substances that change from clear to a color at a specific pH

26. Acids & Bases Titration Curve – graphing pH of solution versus volume of base added M 1 V 1 = M 2 V 2  Used in Acid/Base  Used in Dilution

27. Example Problem: A 100.0mL solution of 0.5M HCl(aq) is titrated with 0.10M NaOH. What volume of NaOH do you need to reach equivalence? M 1 V 1 = M 2 V 2 M HCl V HCl = M NaOH V NaOH (100.0mL HCl)(0.50M HCl) = (X mL NaOH)(0.10M NaOH) X = 500.0mL NaOH Acids & Bases

28. pH – measure of acid strength, equal to the molarity of the H+ ions in solution  1-14 scale  1 = strongest acid  14 = strongest base  7 = neutral  Logarithmic Scale, a change of 1 pH is different in concentration by a factor of 10! pOH – measure of base strength, equal to the molarity of the OH- ions in solution Acids & Bases

29. Useful pH Equations:  pH = -Log[H+]  pOH = -Log[OH-]  14 = pH + pOH  [H+] = 10 (-pH)  [OH-] = 10 (-pOH)  [OH-] [H+] = 1 x 10 -14  [ ] = symbol of Molarity

30. Oxidation – Reduction Reactions 3 – Single Replacement Reactions 4 – Synthesis 5 – Decomposition 6 – Combustion Reactions

31. Oxidation - Reduction Oxidation/Reduction Reaction – a reaction that involves the transfer of electrons  Usually between a metal and nonmetal to form an ionic compound  Involves 2 half reactions Oxidation – loosing electrons Reduction – gaining electrons Potassium.mov zinc&iodine.mov

32. Oxidation - Reduction

33.  2 Mg (s)+O 2 (g) → 2 MgO (s)  Oxidation Mg → Mg 2+ + 2e-  Reduction O 2 + 4e- → 2O 2- Oxidation - Reduction

34. Single Replacement Reaction – Single element combines with a compound, replacing one of the members of the compound. A + BC → AC + B Oxidation – Reduction: (#3) Single Replacement

35. Activity / Electromotive Series Metals Nonmetals lithium fluorine potassium chlorine calcium bromine sodium iodine magnesium aluminum zinc chromium iron nickel tin lead hydrogen copper silver mercury platinum gold Used to predict if a red-ox reaction will occur Metals replace metals. Nonmetals replace nonmetals. The replacing substance must be more active (higher on the list) than the substance it replaces for a reaction to occur. Oxidation – Reduction

36. Predict if a chemical reaction will occur in the following redox reactions: iron + copper (II) sufate  chlorine + potassium bromide  copper + zinc chloride  Oxidation - Reduction

37. Oxidation – Reduction: (#4)Synthesis + (#5)Decomposition Synthesis – Elements combining to make a compound  A + B → AB  Synthesis.MOV Synthesis.MOV Decomposition – Compound separating into its constituent elements  AB → A + B  Decomposition.MOV Decomposition.MOV

38. Combustion Reactions – any reaction that consumes carbon and oxygen to produce carbon dioxide and water General Form: C x H y + O 2 → CO 2 + H 2 O Example: CH 4 + 2O 2 → CO 2 + 2H 2 O Formation of a Gas: Combustion Reactions

39. Top 4 Reactions  Single Replacement  Double Displacement  Synthesis  Decomposition  Four Types.mov Four Types.mov  sugar_potassiumchlorate.mov sugar_potassiumchlorate.mov Other Ways to Classify Reactions

40. Review – Types of Reactions and Driving Forces Double Displacement AB + CD → AD + CB  Acid Base – Formation of water  Multiple - Formation of gas  Precipitation - Formation of a solid Oxidation-Reduction – Driving force for all is transfer of electrons  Single Replacement A + BC → AC + B  Synthesis A + B → AB  Decomposition AB → A + B  Combustion C x H y + O 2 → CO 2 + H 2 O

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