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Reactions in Aqueous Solutions

This chapter reviews basic types of chemical reactions in aqueous solutions including synthesis, decomposition, single replacement, and double replacement reactions. It delves into advanced reaction types like precipitation reactions, discussing how to predict products and differentiate between solubility rules. The text explores three types of equations - molecular, complete ionic, and net ionic - with examples and explanations provided. It also covers acid-base reactions and oxidation-reduction (redox) reactions in detail, emphasizing the importance of oxidation states and the transfer of electrons in chemical reactions.

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Reactions in Aqueous Solutions

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  1. Reactions in Aqueous Solutions Chapter 7

  2. Basic Types of Equations (Review of yesterday’s notes)

  3. Synthesis element + element  compound A+XAX aluminum + oxygen  ? analogy=?

  4. Decomposition compound  element + element AXA+X water? analogy=?

  5. Single Replacement compound and element element and compound AX+BA+BX chromium nitrate + copper ? analogy=?

  6. Double Replacement compound and compound  compound and compound AX+BYAY+BX Silver carbonate + magnesium phosphate? analogy=?

  7. What type of reaction begins with one compound?

  8. Decomposition

  9. What type of reaction begins with one compound and one element?

  10. Single Replacement

  11. What type of reaction begins with two elements?

  12. Composition or Synthesis

  13. What type of reaction begins with two compounds?

  14. Double Displacement

  15. Advanced Types

  16. Types of Reactions I. Precipitation reactions When aqueous solutions of ionic compounds are poured together a solid forms. A solid that forms from mixed solutions is a precipitate. If you’re not a part of the solution, your part of the precipitate.

  17. Precipitation reactions 3NaOH(aq) + FeCl3(aq)3NaCl(aq) + Fe(OH)3(s) is really 3Na+(aq)+3OH-(aq) + Fe+3(aq) + 3Cl-(aq)  3Na+ (aq) + 3Cl- (aq) + Fe(OH)3(s) So all that really happens is 3OH-(aq) + Fe+3(aq)  Fe(OH)3(s) Double replacement reaction

  18. Precipitation reaction We can predict the products Can only be certain by experimenting The anion and cation switch partners AgNO3(aq) + KCl(aq)?

  19. Precipitations Reactions Only happen if one of the products is insoluble Otherwise all the ions stay in solution- nothing has happened.

  20. Solubility Rules (p170) All nitrates are soluble Alkali metals ions and NH4+ ions are soluble Halides are soluble except Ag+, Pb+2, and Hg2+2 Most sulfates are soluble, except Pb+2, Ba+2, Hg+2,and Ca+2

  21. Solubility Rules Most hydroxides are slightly soluble (insoluble) except NaOH and KOH Sulfides, carbonates, chromates, and phosphates are insoluble

  22. Three Types of Equations 1) Molecular Equation- written as whole formulas, not the ions. K2CrO4(aq) + Ba(NO3)2(aq)2KNO3(aq)+BaCrO4(s) 2) Complete Ionic equationshow dissolved electrolytes as the ions. 2K+(aq) + CrO4-2(aq) + Ba+2(aq) + 2 NO3-(aq)  BaCrO4(s)+ 2K+ (aq) + 2 NO3- (aq) Spectator ions are those that don’t react.

  23. Three Type of Equations 3) Net Ionic equations show only those ions that react, not the spectator ions Ba+2 (aq) + CrO4-2 (aq)  BaCrO4(s) Write the three types of equations for the reactions when these solutions are mixed. iron (III) sulfate and potassium sulfide

  24. Answer iron (III) sulfate and potassium sulfide Molecular Fe2(SO4)3 (aq) + 3K2S (aq) Fe2S3 (s) + 3K2SO4 (aq) In your book, rule 2 trumps rule 6. Ionic 2Fe+3 (aq) + 3SO4-2 (aq) + 6K+1 (aq) + 3S-2 (aq) Fe2S3 (s) + 6K+1 (aq) + 3SO4-2 (aq) Net Ionic 2Fe+3 (aq) + 3S-2 (aq) Fe2S3 (s)

  25. Types of Reactions II. Acid-Base Acid + Base salt + water H+ + OH- H2O (often called a neutralization reaction). For our purposes an acid is a proton donor. A base is a proton acceptor usually OH- What is the net ionic equation for the reaction of HCl(aq) and KOH(aq)?

  26. Types of Reaction III. Oxidation-Reduction called Redox Ionic compounds are formed through the transfer of electrons. An Oxidation-reduction reaction involves the transfer of electrons. We need a way of keeping track.

  27. Oxidation States A way of keeping track of the electrons. Not necessarily true of what is in nature, but it works. Need the rules for assigning (memorize). The oxidation state of elements in their standard states is zero. Oxidation state for monoatomic ions are the same as their charge.

  28. Oxidation states Oxide is assigned an oxidation state of -2 in its covalent compounds except as a peroxide. In compounds with nonmetals hydrogen is assigned the oxidation state +1. In its compounds fluoride is always –1. 6 The sum of the oxidation states must be zero in compounds or equal the charge of the ion.

  29. Oxidation States Assign the oxidation states to each element in the following. CO2 NO3- H2SO4 Fe2O3 Fe3O4

  30. Oxidation StatesAssign the oxidation states to each element in the following. +4 -2 CO2 +5 -2 NO3 - +1+6-2 H2SO4 +3 -2 Fe2O3 +2.66 -2 Fe3O4 is actually Fe+3Fe+3Fe+2

  31. Transfer of electrons • Oxidation-loss of electrons • Reduction-gain of electrons • Oxidation/reduction reaction-metal/nonmetal reaction (sometimes nonmetals undergo ox/red if oxygen is a reactant) • 2Na(s)+Cl2(g)2NaCl(s) • Na + Cl Na++ Cl- oxidation reduction

  32. Oxidation-Reduction Transfer electrons, so the oxidation states change. 0 0 +1 -1 Na + 2Cl2 2NaCl +4 -1 0 +4-2 +1 -2 CH4 + 2O2 CO2+ 2H2O Oxidation is the loss of electrons. Reduction is the gain of electrons. OIL RIG LEO GER

  33. Oxidation-Reduction Oxidation means an increase in oxidation state - lose electrons. Reduction means a decrease in oxidation state - gain electrons. The substance that is oxidized is called the reducing agent. The substance that is reduced is called the oxidizing agent.

  34. Identify the Oxidizing agent Reducing agent Substance oxidized Substance reduced Fe(s) + O2(g)  Fe2O3(s) Fe2O3(s)+ 3 CO(g)  2 Fe(l) + 3 CO2(g)

  35. Combustion Reaction of a hydrocarbon/alcohol or other organic molecule with oxygen gas to produce carbon dioxide and water C3H8 + 5 O2→ 3 CO2 + 4 HOH CH3CH2OH + 3 O2 → 2 CO2 + 3 HOH

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