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Aqueous Reactions and Solution Stoichiometry

Aqueous Reactions and Solution Stoichiometry. Aqueous Solutions. Solutions in which water is the dissolving medium. Water Molecule. Hydrogen Bonds. High surface tension Low vapor pressure High specific heat capacity High heat of vaporization High boiling point.

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Aqueous Reactions and Solution Stoichiometry

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  1. Aqueous Reactions and Solution Stoichiometry

  2. Aqueous Solutions • Solutions in which water is the dissolving medium

  3. Water Molecule

  4. Hydrogen Bonds

  5. High surface tension Low vapor pressure High specific heat capacity High heat of vaporization High boiling point Properties of Water Resulting from Hydrogen Bonding

  6. Solvents and Solutes • Aqueous Solutions: Water samples containing dissolved substances • Solute: the dissolved particles • Solvent: The medium the particles dissolve in • Solutions are homogeneous mixtures • Solutes can be solids, liquids or gases- ionic or molecular

  7. Solvation: the process that occurs when a solute dissolves H2O and NaCl H2O and Oil Like Dissolves Like

  8. Solutions • Homogeneous mixtures of solids, liquids, or gasses

  9. Factors that affect Solubility • Nature of the solvent and solute • Agitation (stirring) • Temperature • Surface Area

  10. Agitation • Affects only the rate of dissolution not the amount

  11. The higher the temperature the higher the solubility Higher temperatures= greater kinetic energy = increased frequency of collisions between solute and solvent Temperature

  12. Temperature vs. Solubility

  13. Surface Area • Fine powders will dissolve more rapidly than large crystals • Dissolving is a surface phenomenon • More surface = faster dissolution

  14. Solubility • Is the amount of a substance that dissolves in a given quantity of a solvent at a given temperature

  15. A solution that contains the maximum amount of solute for a given amount of solvent at a constant temperature Saturated Solution

  16. Unsaturated • Contains less solute than a saturated solution

  17. Solubility of liquids • Miscible: Two liquids that dissolve in each other (i.e. Ethanol and water) • Immiscible: two liquids that are completely insoluble (i.e. Oil and water)

  18. Solubility http://phet.colorado.edu

  19. Concentration • Concentration of a solution is expressed as the amount of solute dissolved in an amount of solution • Dilute solution: contains a low concentration of solute • Concentrated Solution: contains a high concentration of solute

  20. Concentration

  21. Molarity • Molarity (M) is the number of moles of solute dissolved per liter of solution • Volume is the total volume of the solution, NOT the volume of the solvent alone

  22. Molarity • Molarity (M) = Moles of solute Liter of solution

  23. Example • A solution has a volume of 250 mL and contains 0.70 mol NaCl. What is the molarity of the solution? • Molarity (M) = Moles of solute Liter of solution

  24. Example • A solution has a volume of 2.0 L and contains 36.0 g of glucose. If the molar mass of glucose is 180 g/mol what is the molarity of the solution? Molarity (M) = Moles of solute Liter of solution

  25. Making Dilutions • You can make a solution less concentrated by diluting it with solvent • The dilution reduces the moles of solute per unit volume • Total moles of solute does not change • Moles of solute = moles of solute before dilution after dilution

  26. Dilution • M1V1=M2V2 • M= molarity • V= volume

  27. Example • How many milliliters of a stock solution of 4.00 M KI would you need to prepare 250.0 mL of 0.760 M KI? • M1V1=M2V2

  28. Electrolytes: compounds that conduct electricity in aqueous solution or molten state ALL Ionic compounds are electrolytes Not all conduct to the same degree Nonelectrolytes: don’t conduct Electrolytes and Nonelctrolytes

  29. Acids • Give food a sour flavor • Aqueous solutions of acids are electrolytes • React with compounds containing hydroxide ions to form salt and water

  30. Formulas of Acids • An acid produces hydrogen ions- generic acid HX (X is an ion) • IE • HCl • H2SO4 • HNO3

  31. Common Triprotic Acids • H3PO4 Phosphoric Acid

  32. Strong Acids • Strong acids are completely ionized in an aqueous solution • Hydrochloric Acid • Sulfuric Acid • HCl (g) + H2O (l) H3O+ (aq) + Cl- (aq)

  33. Weak Acids • Weak acids ionize only slightly in aqueous solution, ionization is not complete • CH3COOH (aq) + H2O H3O+(aq) + CH3COO- (aq) • Ethanoic Acid Ethonate ion <1%

  34. Bases • Feel slippery • Taste bitter • Are electrolytes • React with acids to form water and salt

  35. Strong Bases • Strong bases dissociate completely into metal ions and hydroxide ions in aqueous solutions • ALL bases containing OH- ions are strong bases

  36. Weak Bases • Weak bases react with water to form the hydroxide ion and the conjugate acid of the base • NH3 (aq) + H2O (l) NH4+ (aq) + OH- (aq) • <1%

  37. The concentration of an acid (or base) in a solution can be determined by performing a neutralization reaction Titration

  38. Steps for Titration • A measured volume of an acidic solution is added to a flask

  39. Steps for Titration • Several drops of the indicator are added to the solution

  40. Measured volumes of a base of known concentration are mixed into the acid until the indicator barely changes color Steps for Titration

  41. The solution of known concentration Standard Solution Standard Solution

  42. End Point • The point at which the indicator changes color

  43. Equivalence Point

  44. Equivalent • Is the amount of acid (or base) that will give 1 mole of hydrogen (or hydroxide) ions

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