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![Example: 4.2
Predict what happens when a potassium phosphate (K3PO4) solution is
mixed with a calcium nitrate [Ca(NO3)2] solution. Write a net ionic
equation for the reaction.](https://image.slidesharecdn.com/reactionsinaqueoussolutions-251005183937-cd044ea5/75/Reactions-in-Aqueous-Solutions-introduction-pptx-17-2048.jpg)
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Reactions in Aqueous Solutions introduction.pptx
- 1. Reactions in AqueousSolutions Chapter 4
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- 4. 4 A solution isa homogenous mixture of 2 or more substances. The solute is (are) the substance(s) present in the smaller amount(s). The solvent is the substance present in the larger amount. Solution Solvent Solute Soft drink (l) Air (g) Soft solder (s) H2O N2 Pb Sugar, CO2 O2, Ar, CH4 Sn aqueous solutions of KMnO4
- 5. Conduct electricity insolution? Cations (+) and Anions (-) ELECTROLYTE
- 6. An electrolyte isa substance that, when dissolved in water, results in a solution that can conduct electricity. A nonelectrolyte is a substance that, when dissolved, results in a solution that does not conduct electricity.
- 7. Hydration Strong Electrolyte –100% dissociation NaCl (s) Na+ (aq) + Cl- (aq) H2O d+ d- H2O process in which an ion is surrounded by water molecules arranged in a specific manner.
- 8. HCl(l) H+ (aq) +Cl− (aq) CH3COOH(aq) H+ (aq) + CH3COO− (aq) Weak Electrolyte – not completely dissociated
- 9. Review of Concepts Thediagrams here show three compounds AB2 (a), AC2 (b), and AD2 (c) dissolved in water. Which is the strongest electrolyte and which is the weakest? (For simplicity, water molecules are not shown.)
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- 11. Precipitate – insolublesolid that separates from solution CdS PbS Ni(OH)2 Al(OH)3
- 12. Solubility is themaximum amount of solute that will dissolve in a given quantity of solvent at a specific temperature.
- 13. Example: 4.1 Classify thefollowing ionic compounds as soluble or insoluble: (a) silver sulfate (Ag2SO4) (b) calcium carbonate (CaCO3) (c) sodium phosphate (Na3PO4).
- 15. 15 molecular equation ionic equation netionic equation Pb2+ + 2NO3 - + 2Na+ + 2I- PbI2 (s) + 2Na+ + 2NO3 - Na+ and NO3 - are spectator ions PbI2 Pb(NO3)2 (aq) + 2NaI (aq) PbI2 (s) + 2NaNO3 (aq) precipitate Pb2+ + 2I- PbI2 (s)
- 16. 16 Writing Net IonicEquations 1. Write the balanced molecular equation. 2. Write the ionic equation showing the strong electrolytes completely dissociated into cations and anions. 3. Cancel the spectator ions on both sides of the ionic equation. 4. Check that charges and number of atoms are balanced in the net ionic equation.
- 17. Example: 4.2 Predict whathappens when a potassium phosphate (K3PO4) solution is mixed with a calcium nitrate [Ca(NO3)2] solution. Write a net ionic equation for the reaction.
- 18. Review of Concepts Whichof the diagrams here accurately describes the reaction between Ca(NO3)2(aq) and Na2CO3(aq)? For simplicity, only the Ca2+ (yellow) and CO3 2− (blue) ions are shown.
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- 20. ACID • Sour taste •Color changes in plant dyes • React with metals to produce H2 gas • React with carbonates and bicarbonates to produce CO2 gas • Aqueous acid solutions conduct electricity • Taste bitter • Feel slippery • Color changes in plant dyes • Aqueous base solutions conduct electricity BASE General Properties
- 21. 21 Arrhenius acid isa substance that produces H+ (H3O+ ) in water. Arrhenius base is a substance that produces OH- in water.
- 22. ACID • Proton donor• Proton acceptor BASE Brønsted Acid and Bases acid base acid base A Brønsted acid must contain at least one ionizable proton!
- 23. 23 Monoprotic acids HCl H+ +Cl- HNO3 H+ + NO3 - CH3COOH H+ + CH3COO- Strong electrolyte, strong acid Strong electrolyte, strong acid Weak electrolyte, weak acid Diprotic acids H2SO4 H+ + HSO4 - HSO4 - H+ + SO4 2- Strong electrolyte, strong acid Weak electrolyte, weak acid Triprotic acids H3PO4 H+ + H2PO4 - H2PO4 - H+ + HPO4 2- HPO4 2- H+ + PO4 3- Weak electrolyte, weak acid Weak electrolyte, weak acid Weak electrolyte, weak acid
- 24. STRONG ACIDS HI HBr HClO4 HCl H2SO4 HNO3 NaOH KOH LiOH RbOH CsOH Ca(OH)2 Ba(OH)2 Sr(OH)2 STRONG BASES Strongacids/bases are strong electrolytes and will completely dissociate in water.
- 25. Example: 4.3 Classify eachof the following species in aqueous solution as a Brønsted acid or base: (a) HBr (b) (c)
- 26. Review of Concepts Whichof the following diagrams best represents a weak acid? Very weak acid? Strong acid? The proton exists in water as the hydronium ion. All acids are monoprotic. (For simplicity, water molecules are not shown.)
- 27. Acid-Base Neutralization acid +base salt + water HCl (aq) + NaOH (aq) NaCl (aq) + H2O H+ + Cl- + Na+ + OH- Na+ + Cl- + H2O H+ + OH- H2O (l) (l)
- 28. 28 Neutralization Reaction Involvinga Weak Electrolyte weak acid + base salt + water HCN (aq) + NaOH (aq) NaCN (aq) + H2O HCN + Na+ + OH- Na+ + CN- + H2O HCN + OH- CN- + H2O
- 29. Example: 4.4 Write molecular,ionic, and net ionic equations for each of the following acid-base reactions: (a) hydrobromic acid(aq) + barium hydroxide(aq) (b) sulfuric acid(aq) + potassium hydroxide(aq)
- 30. Gas formation • Certainsalts react with acids to produce gaseous products • 2 HNO2 breaks down into H2O(l) + NO2(g) + NO(g) • H2CO3 breaks down into H2O(l) + CO2(g) • H2SO3 breaks down into H2O(l) + SO2(g) • NH4OH breaks down into H2O(l) + NH3(g) • H2S(g) • CO2(g) • H2(g) • If you get one of these as a product in your molecular equation, they immediately breakdown as above • Gasses do not ionize
- 31. 2HCl (aq) +Na2CO3 (aq) 2NaCl (aq) + H2O +CO2 2H+ + 2Cl- + 2Na+ + CO3 2- 2Na+ + 2Cl- + H2O + CO2 2H+ + CO3 2- H2O + CO2
- 32. Double Replacement Rxns Review DrivingForce How do you recognize it? Precipitate You must memorize the solubility rules. Any compound formed from two ions can be recognized as soluble (written as separate ions) or as a precipitate (written as a molecule). Gas formed You must memorize the combinations that decompose into gases (there are 4). You must also memorize the gases that form. For example, when you H2SO3 as a product, you must know it decomposes into H2O and SO2 gas. Weak electrolyte You must memorize the short list of strong acids and strong bases so you will recognize all the weak acids and bases that dissolve, but do not dissociate into ions. The weak base ammonia, NH3, is in this category. It exits in water as NH3(aq) and only slightly forms the
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- 34. OXIDATION REACTION • Reactionthat involves the loss of electrons • Contains reducing agent- donates electrons • Oxidation number becomes more positive • Electrons are on the product side of the half reaction • Involves the gain of electrons • Contains oxidizing agent- accepts electrons • Oxidation number becomes more negative • Electrons are on the reactant side of the half reaction REDUCTION REACTION Half-reaction OIL RIG 2Mg 2Mg2+ + 4e- O2 + 4e- 2O2- 2Mg + O2 + 4e- 2Mg2+ + 2O2- + 4e-
- 35. 35 Zn(s) + CuSO4(aq)ZnSO4(aq) + Cu(s) Zn is oxidized Zn Zn2+ + 2e- Cu2+ is reduced Cu2+ + 2e- Cu Zn is the reducing agent Cu2+ is the oxidizing agent
- 36. Oxidation Number • Chargethe atom would have in a molecule if electrons were transferred completely • Rules • Uncombined elements = 0 • Neutral compounds sum = 0 • Ion = ion charge (polyatomic ions sum to charge) • Exceptions • Hydrogen +1 w/ nonmetals, −1 w/ metals • Oxygen −2 except w/ fluorine (+2), in peroxides (−1) • Fluorine ALWAYS −1
- 37. Example: 4.5 Assign oxidationnumbers to all the elements in the following compounds and ion: (a) Li2O (b) HNO3 (c)
- 38. More common oxidation numbersare in red.
- 39. 39 Combination Reaction A +B C 2Al + 3Br2 2AlBr3 Decomposition Reaction 2KClO3 2KCl + 3O2 C A + B 0 0 +3 -1 +1 +5 -2 +1 -1 0 Types of Redox Reactions
- 40. 40 Combustion Reaction A +O2 B S + O2 SO2 0 0 +4 -2 2Mg + O2 2MgO 0 0 +2 -2
- 41. 41 Displacement Reaction A +BC AC + B Sr + 2H2O Sr(OH)2 + H2 TiCl4 + 2Mg Ti + 2MgCl2 Cl2 + 2KBr 2KCl + Br2 Hydrogen Displacement Metal Displacement Halogen Displacement 0 +1 +2 0 0 +4 0 +2 0 -1 -1 0
- 42. Activity Series For Halogens: F2> Cl2 > Br2 > I2
- 43. 43 The same elementis simultaneously oxidized and reduced. Example: Disproportionation Reaction Cl2 + 2OH- ClO- + Cl- + H2O 0 +1 -1 oxidized reduced
- 44. Elements most likelyto undergo disproportionation
- 45. Example: 4.6 Classify thefollowing redox reactions and indicate changes in the oxidation numbers of the elements: (a) (b) (c) (d)
- 46. Concentration Molarity = molesof solute liters of solution n V M = KCl(s) K+ (aq) + Cl− (aq) H2O Ex: 1M KCl solution Ex: 1M Ba(NO3)2 solution Ba(NO3)2(s) Ba2+ (aq) + 2 NO3 − (aq) H2O
- 47. 47 Preparing a Solutionof Known Concentration
- 48. Example: 4.7 How manygrams of potassium dichromate (K2Cr2O7) are required to prepare a 250-mL solution whose concentration is 2.16 M? A K2Cr2O7 solution.
- 49. Example: 4.8 In abiochemical assay, a chemist needs to add 3.81 g of glucose to a reaction mixture. Calculate the volume in milliliters of a 2.53 M glucose solution she should use for the addition.
- 50. Dilution procedure for preparinga less concentrated solution from a more concentrated solution. Dilution Add Solvent Moles of solute before dilution (i) Moles of solute after dilution (f) = MiVi MfVf =
- 51. Example: 4.9 Describe howyou would prepare 5.00 × 102 mL of a 1.75 M H2SO4 solution, starting with an 8.61 M stock solution of H2SO4.
- 52. Review of Concepts Whatis the final concentration of a 0.6M NaCl solution if its volume is doubled and the number of moles of solute is tripled?
- 53. Quantitative analysis • Gravimetricanalysis • Titrations • Acid-base • redox
- 54. 1. Dissolve unknownsubstance in water 2. React unknown with known substance to form a precipitate 3. Filter and dry precipitate 4. Weigh precipitate 5. Use chemical formula and mass of precipitate to determine amount of unknown ion Gravimetric Analysis
- 55. Example: 4.10 A 0.5662-gsample of an ionic compound containing chloride ions and an unknown metal is dissolved in water and treated with an excess of AgNO3. If 1.0882 g of AgCl precipitate forms, what is the percent by mass of Cl in the original compound?
- 56. 56 Titrations In a titration,a solution of accurately known concentration is added gradually added to another solution of unknown concentration until the chemical reaction between the two solutions is complete. Equivalence point – the point at which the reaction is complete Indicator – substance that changes color at (or near) the equivalence point Slowly add base to unknown acid UNTIL the indicator changes color
- 57. 57 Titrations can beused in the analysis of Acid-base reactions Redox reactions H2SO4 + 2NaOH 2H2O + Na2SO4 5Fe2+ + MnO4 - + 8H+ Mn2+ + 5Fe3+ + 4H2O
- 58. Example: 4.11 In atitration experiment, a student finds that 23.48 mL of a NaOH solution are needed to neutralize 0.5468 g of KHP. What is the concentration (in molarity) of the NaOH solution?
- 59. Example: 4.12 How manymilliliters (mL) of a 0.610 M NaOH solution are needed to neutralize 20.0 mL of a 0.245 M H2SO4 solution?
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- 61. Example: 4.13 A 16.42-mLvolume of 0.1327 M KMnO4 solution is needed to oxidize 25.00 mL of a FeSO4 solution in an acidic medium. What is the concentration of the FeSO4 solution in molarity? The net ionic equation is