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Chapter 8 Reactions in Aqueous Solution

Chapter 8 Reactions in Aqueous Solution. Will a reaction Occur?. Driving Forces in a Chemical Reaction Formation of a solid Formation of water Formation of a gas Transfer of electrons. Types of Reactions. Double Replacement Reactions 1. Precipitation Reactions

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Chapter 8 Reactions in Aqueous Solution

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

  6. Solid Formation: Precipitation Reactions (#1) Precipitation Reaction – a reaction that produces a precipitate • K2CrO4 (aq) + Ba(NO3)2 (aq) → BaCrO4 (s) + 2 KNO3 (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(NO3)2(aq)→ Ba2+ (aq)+ 2 NO31- (aq) • Strong Electrolyte – completely dissociates into ions in solution (dissolving.mov) • The reaction is best demonstrated by: 2 K1+ (aq)+ CrO42-(aq)+ Ba2+(aq) + 2 (NO3)1-(aq)→ BaCrO4 (s) + 2 K1+ (aq)+ 2 NO31-(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 – • NO3- salts • Na+, K+, NH4+ salts • Cl-, Br-, I- salts, but not when with Ag+, Hg22+, and Pb2+ • SO42- salts, but not when with Ba2+ , Pb2+, and Ca2+

  10. Solid Formation - Solubility Rules • Insoluble • S2- • CO32- • PO43- • OH-, but not when with Na+, K+, Ca2+

  11. Visualizing Solubility

  12. Describing reactions in Aqueous Solutions • Molecular Equation – Represents allmolecules 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(NO3)2(aq) + Na2SO4(aq)→ PbSO4(s) + 2NaNO3(aq) Net Ionic Equation • Pb2+(aq) + SO42-(aq)→ PbSO4(s) Complete Ionic Equation • Pb2+(aq) + 2(NO3)-(aq) + 2Na1+ (aq)+SO42-(aq)→ PbSO4(s) + 2Na+ (aq) + 2NO3-(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) → H1+ (aq) + Cl1- (aq)

  16. Formation of Water: (#2) Acids & Bases • 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) → Na1+ (aq) + OH1- (aq)

  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

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

  19. Acids & Bases • 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

  20. Acids & Bases Acid + Base → Conjugate Acid + Conjugate Base H2SO4 + NaOH → H2O + Na2SO4 To find the conjugate acid – follow the hydrogen To find the conjugate base - follow the anion from the acid

  21. Acids & Bases • 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

  22. Acids & Bases • 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

  23. 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 Acids & Bases

  24. Titration Curve – graphing pH of solution versus volume of base added M1V1 = M2V2 Used in Acid/Base Used in Dilution Acids & Bases

  25. Acids & Bases • 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 MHClVHCl = MNaOHVNaOH (100.0mL HCl)(0.50M HCl) = (X mL NaOH)(0.10M NaOH) X = 500.0mL NaOH

  26. Acids & Bases • 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

  27. 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 Acids & Bases

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

  29. 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

  30. Oxidation - Reduction

  31. Oxidation - Reduction • 2 Mg (s)+O2 (g) → 2 MgO (s) • Oxidation • Mg → Mg 2+ + 2e- • Reduction • O2 + 4e- → 2O2-

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

  33. 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

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

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

  36. Formation of a Gas: Combustion Reactions • Combustion Reactions – any reaction that consumes carbon and oxygen to produce carbon dioxide and water • General Form: CxHy + O2→ CO2 + H2O • Example: CH4 + 2O2→ CO2 + 2H2O

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

  38. 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 CxHy + O2→ CO2 + H2O

  39. If you need help, please schedule tutoring – the best time is after school!!! GOOD LUCK

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