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Exam W 10/28

Exam W 10/28. Review T 10/27 1 pm SL 150. Happy Mole Day!. Precipitation. Solubility. Soluble = ability to dissolve in a liquid Insoluble = inability to dissolve in a liquid Not all Ionic Compounds are water soluble Not all molecular compounds are insoluble!.

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Exam W 10/28

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  1. Exam W 10/28 Review T 10/27 1 pm SL 150

  2. Happy Mole Day!

  3. Precipitation

  4. Solubility • Soluble = ability to dissolve in a liquid • Insoluble = inability to dissolve in a liquid • Not all Ionic Compounds are water soluble • Not all molecular compounds are insoluble!

  5. 8 Simple Rules For Common Ionic Compounds

  6. Song For Solubility!! (Taken from Cornell University – Adapted by Daley – Sing to Rhythm of 99 Bottles)  Potassium, sodium, and ammonium salts,  Whatever they may be, Can always be depended on For solubility. Asked about the nitrates or acetates The answer is always clear, They each and all are soluble, Is all we want to hear.  Most every chloride's soluble At least we've always read Save silver, mercurous mercury And (slightly) chloride of lead. Take the Bromide and iodide salts There soluble as can be Save silver, mercury, and lead That precipitate as you see Every single sulfate Is soluble ,  'Tis said 'Cept barium and strontium And calcium and lead.  Hydroxides of metals won't dissolve That is, all but three Potassium, sodium and ammonium Dissolve quite readily. And then you must remember That you must not "forgit" Calcium, barium, strontium Dissolve a little bit.  The carbonates are insoluble,  It's lucky that it's so, Or else, our marble buildings Would melt away like snow.  (Repeat with feeling)  Only note is that all Lithium salts are Soluble too!!!

  7. Reactions Involving Ions:Molecular vs. Ionic Equations • Chemical Reaction can be expressed by: • Molecular Equation (balanced chemical equation) • Complete Ionic Equation (showing all ions in reaction) • Net Ionic Equation (showing only those ions directly involved in reaction) • Consider Copper (III) sulfate reacts with sodium hydroxide to form copper (III) hydroxide and sodium sulfate (all in water). • Express reaction in molecular, complete ionic, • and net ionic equations

  8. Predicting Whether a Precipitation Reaction Occurs; Writing Equations: a) Calcium Nitrate and Sodium Sulfate solutions are added together. Molecular Equation Ca(NO3)2 (aq) + Na2SO4 (aq) CaSO4 (s) + 2NaNO3 (aq) Total Ionic Equation Ca2+(aq)+2 NO3-(aq) + 2 Na+(aq)+ SO4-2(aq) CaSO4 (s) + 2 Na+(aq+) 2 NO3-(aq) Net Ionic Equation Ca2+(aq) + SO-2(aq) CaSO4 (s) Spectator Ions are Na+ and NO3- b) Ammonium Sulfate and Magnesium Chloride are added together. In exchanging ions, no precipitates will be formed, so there will be no chemical reactions occurring! All ions are spectator ions!

  9. Figure 4.6: Reaction of magnesium chloride and silver nitrate. Photo courtesy of American Color. Write molecular and ionic equations for this reaction. Ionic equation: Ag+(aq) + Cl-(aq) AgCl(s)

  10. Oxidation-Reduction 2Na (s) + Cl2(g) 2NaCl(s) Oxidation numbers

  11. Figure 4.10: Iron nail and copper ( II) sulfate.Photo courtesy of American Color.

  12. Figure 4.10: Fe reacts with Cu2+(aq) and makesCu(s).Photo courtesy of American Color.

  13. Figure 4.10: The copper metal plates out on the nail.Photo courtesy of American Color. Write a net ionic equation for this reaction! Cu+2(aq) + Fe(s) Cu(s) + Fe+2(aq)

  14. Household Acids and Bases

  15. Definition of Acid & Base • Arrhenius • Acid: substance that produces H+ ions • Base: substance that produces OH- ions • Bronsted & Lowry • Acid: substance that donates a proton to another substances • Base: substance that accepts a proton to another substances

  16. Acids - A Group of Covalent Molecules Which Lose Hydrogen Ions to Water Molecules in Solution When gaseous hydrogen iodide dissolves in water, the attraction of the oxygen atom of the water molecule for the hydrogen atom in HI is greater that the attraction of the of the iodide ion for the hydrogen atom, and it is lost to the water molecule to form an hydronium ion and an iodide ion in solution. We can write the hydrogen atom in solution as either H+(aq) or as H3O+(aq) they mean the same thing in solution. The presence of a hydrogen atom that is easily lost in solution is an “Acid” and is called an “acidic” solution. The water (H2O) could also be written above the arrow indicating that the solvent was water in which the HI was dissolved. HI(g) + H2O(L) H+(aq) + I -(aq) HI(g) + H2O(L) H3O+(aq) + I -(aq) H2O HI(g) H+(aq) + I -(aq)

  17. Figure 4.8B: Red cabbage juice added to solutions in the beakers.Photo courtesy of James Scherer.

  18. Molecular representation of ammonium hydroxide. NH3(aq) + H2O(l) NH4+(aq) + OH-(aq)

  19. Reaction of nitric acid with water. HNO3(aq)+ H2O(l)  NO3-(aq) + H3O+(aq)

  20. Strong Acid or Base An acid or base that ionizes completely in water. It is present entirely as ions; it is a strong electrolyte.

  21. Weak Acid or Base • An acid or base that is only partly ionized in water. It is present primarily as molecules and partly as ions; it is a weak electrolyte. Weak bases are often nitrogen bases such as NH3: • NH3(aq) + H2O(l) →NH4+(aq) + OH-(aq) • The most common weak acid is acetic acid: • HC2H3O2 (aq)+ H2O(l) → H3O+(aq)+ C2H3O2-(aq) • If an acid or base is not strong, it is weak.

  22. Polyprotic Acid • An acid that results in two or more acidic hydrogens per molecule • For example: H2SO4, sulfuric acid

  23. Neutralization Reaction • A reaction of an acid and a base that results in an ionic compound (a salt) and possibly water • Write the molecular, ionic, and net ionic equations for the neutralization of sulfurous acid, H2SO3, by potassium hydroxide, KOH.

  24. Molecular Equation • (Balance the reaction and include state symbols) • H2SO3(aq) + 2KOH(aq)  2H2O(l) + K2SO3(aq) • Ionic Equation • H2SO3(aq) + 2K+(aq) + 2OH-(aq)  • 2H2O(l) + 2K+(aq) + SO32-(aq) • Net Ionic Equation • H2SO3(aq) + 2OH-(aq)  2H2O(l) + SO32-(aq)

  25. Acid-Base Reaction with Gas Formation • Some salts, when treated with an acid, produce a gas. Typically sulfides, sulfites, and carbonates behave in this way producing hydrogen sulfide, sulfur trioxide, and carbon dioxide, respectively. The photo shows baking soda (sodium bicarbonate) reacting with acetic acid in vinegar to give bubbles of carbon dioxide. Write the reaction that’s occurring.

  26. Molarity (Concentration of Solutions)= M Moles of Solute Moles Liters of Solution L M = = solute = material dissolved into the solvent In air , Nitrogen is the solvent and oxygen, carbon dioxide, etc. are the solutes. In sea water , Water is the solvent, and salt, magnesium chloride, etc. are the solutes. In brass , Copper is the solvent (90%), and Zinc is the solute(10%)

  27. Fig. 3.11

  28. Preparing a Solution - I • Prepare a solution of Sodium Phosphate by dissolving 3.95g of Sodium Phosphate into water and diluting it to 300.0 ml or 0.300 l ! • What is the Molarity of the salt and each of the ions? • Na3PO4 (s) + H2O(solvent) = 3 Na+(aq) + PO4-3(aq)

  29. You place a 1.62-g of potassium dichromate, K2Cr2O7, into a 50.0-mL volumetric flask. You then add water to bring the solution up to the mark on the neck of the flask. What is the molarity of K2CrO7 in the solution? Molar mass of K2Cr2O7 is 294 g. 0.110 M

  30. Dilution • When a higher concentration solution is used to make a less-concentration solution, the moles of solute are determined by the amount of the higher-concentration solution. The number of moles of solute remains constant. • MiVi = MfVf • Note: • The units on Vi and Vf must match.

  31. A saturated stock solution of NaCl is 6.00 M. How much of this stock solution is needed to prepare 1.00-L of physiological saline soluiton (0.154 M)?

  32. Titration • A procedure for determining the amount of substance A by adding a carefully measured volume with a known concentration of B until the reaction of A and B is just complete

  33. Figure 4.22C: Titration of an unknown amount of HCl with NaOH (#3). Photo courtesy of American Color.

  34. Titration of an unknown amount of HCl with NaOH. • In the titration above, the indicator changes color to indicate when the reaction is just complete.

  35. Zinc sulfide reacts with hydrochloric acid to produce hydrogen sulfide gas: • ZnS(s) + 2HCl(aq) ZnCl2(aq) + H2S(g) • How many milliliters of 0.0512 M HCl are required to react with 0.392 g ZnS?

  36. Molar mass of ZnS = 97.47 g • = 0.157 L = 157 mL HCl solution

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