Chemistry of solutions


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Chemistry of solutions

  1. 1. D’ CHEMISTRY OF <br />SOLUTIONS<br />
  2. 2. SOME DEFINITIONS<br />A solution is a _______________ mixture of 2 or more substances in a single phase. <br />One constituent is usually regarded as the SOLVENTand the others as SOLUTES.<br />
  3. 3. SOME DEFINITIONS<br /><ul><li>Solutions are homogeneous mixtures of two or more pure substances.
  4. 4. In a solution, the solute is dispersed uniformly throughout the solvent.</li></li></ul><li>PARTS OF A SOLUTION<br />SOLUTE – the part of a solution that is being dissolved <br />(usually the lesser amount)<br />SOLVENT – the part of a solution that dissolves the solute <br />(usually the greater amount)<br />Solute + Solvent = Solution<br />O2<br />N2<br />NH3<br />H2O<br />H2O<br />Isopropyl alcohol<br />H2O<br />Ethyl alcohol<br />Iodine<br />Alcohol<br />H2O<br />Salt<br />
  5. 5. WHICH IS WHICH 1st ROUND<br /><ul><li>Identify the solute and solvent in each of the following solutions.
  6. 6. 1.0 g of sugar dissolved in 100 g of water.
  7. 7. 50 mL of water mixed with 20 mL isopropyl alcohol
  8. 8. A tincture of Iodine is prepared with 0.10 g I2 and 10.0 mL of ethyl alcohol.
  9. 9. 40 % ethanol a rubbing alcohol.
  10. 10. Sugar is the smaller quantity that is dissolving. Therefore it the solute and water is the solvent.
  11. 11. Since both water and isopropyl alcohol are liquids, the one smaller volume, is the solute and water is the solvent.
  12. 12. Iodine is the solute and ethyl alcohol is the solvent.
  13. 13. Ethanol is the solvent and water is the solute. </li></li></ul><li>WHICH IS WHICH 2nd ROUND<br /><ul><li>Identify the solute and solvent in each of the following solutions.
  14. 14. 10 g NaCl and 100 g of water.
  15. 15. 50 mL ethanol and 10 mL H2O
  16. 16. 2.0 L oxygen and 8.0 L nitrogen.
  17. 17. 100 g silver and 40 g mercury.
  18. 18. 100 mL H2O and 5.0 g sugar</li></li></ul><li>TYPE OF SOLUTION<br /><ul><li> Gas
  19. 19. Liquid
  20. 20. Solid</li></li></ul><li>SOME EXAMPLES OF SOLUTION<br />Air<br />Oxygen<br />Nitrogen<br />H2O<br />CO2<br />Soda water<br />H2O<br />Vinegar<br />Acetic acid<br />H2O<br />Sugar <br />Sugar syrup<br />Ag<br />Hg<br />Dental <br />amalgam<br />Brass or <br />Steel<br />Carbon<br />Zinc<br />Iron<br />Copper<br />
  21. 21. D’ UNIVERSAL SOLVENT<br />WATER<br />H2O<br />
  22. 22. HOW SOLUTIONS ARE<br />FORMED?<br />
  23. 23. DEFINE SOLUTIONS<br /><ul><li>Solutions are homogeneous mixtures of two or more pure substances.
  24. 24. In a solution, the solute is dispersed uniformly throughout the solvent.</li></li></ul><li>How Does a Solution Form?<br />Solvent molecules attracted to surface ions.<br />Each ion is surrounded by solvent molecules.<br />Enthalpy (DH) changes with each interaction <br /> broken or formed.<br />Ionic solid dissolving in water<br />
  25. 25. <ul><li>The ions are solvated</li></ul>(surrounded by solvent).<br /><ul><li>If the solvent is water, the ions are hydrated.
  26. 26. The intermolecular forces.</li></ul>How Does a Solution Form?<br />
  27. 27. <ul><li>solvation is an interaction of a solute with the solvent, which leads to stabilization of the solute in the solution.</li></ul>What is solvation?<br />
  28. 28. KINDS OF SOLUTION<br /><ul><li>Dilute</li></ul> small amount of solute dispersed in the solvent<br /><ul><li>Concentrated</li></ul> large amount of solute is dissolved in the solvent<br />
  29. 29. Types of Solutions Based on Solute Concentration…<br /><ul><li>Hypotonic</li></ul> (lower solute concentration) to the solution<br /><ul><li>Hypertonic</li></ul> (higher solute concentration) to the solution<br />
  30. 30. <ul><li>Isotonicsolutions are equal in their solute concentrations. We say that they</li></ul> are isotonic to each other.<br />Types of Solutions Based on Solute Concentration…<br />
  31. 31. QUESTIONS THAT NEEDS SOLUTIONS…<br /><ul><li>How does a solid dissolve into a liquid?
  32. 32. What ‘drives’ the dissolution process?
  33. 33. What are the energetics of dissolution?</li></li></ul><li>WHAT IS DISSOLUTION ?<br />is the process by which a solid, <br /> liquid or gas <br /> forms a solution <br /> in a solvent.<br />
  34. 34. DISSOLUTION PROCESS IN SOLIDS…<br />In solids this can be explained as the breakdown of the crystal lattice into individual ions, atoms or molecules and their transport into the solvent.<br />
  35. 35. DISSOLUTION PROCESS IN LIQUIDS & GASES…<br />For liquids and gases, the molecules must be compatible with those of the solvent for a solution to form.<br />
  36. 36. dry<br />Dissolution vs Reaction<br />NiCl2(s)<br />Ni(s) + HCl (aq)<br />NiCl2(aq) + H2(g)<br />Dissolution is a physical change—you can get back the original solute by evaporating the solvent.<br />If you can’t, the substance didn’t dissolve, it reacted.<br />
  37. 37. DEFINE<br />SOLUBILITY?<br />
  38. 38. What is Solubility?<br />refers to the maximum amount of solute, expressed in grams, that can be dissolved in 100 g of water at a specific temperature & pressure.<br />
  39. 39. <ul><li>Soluble </li></ul> a substance that dissolves in a solvent<br /><ul><li>Insoluble </li></ul> a substance that does not dissolve in a solvent (sand is insoluble in water)<br />VOCABULARY<br />
  41. 41. VOCABULARY<br /><ul><li>Immiscible</li></ul> Two liquids that are insoluble <br />(Oil & Vinegar)<br /><ul><li>Miscible</li></ul> Two liquids that are soluble in each other <br />(Alcohol & Water)<br />IMMISCIBLE<br />MISCIBLE<br />MISCIBLE<br />S/MISCIBLE<br />
  42. 42. <ul><li>Saturated solution
  43. 43. Solvent holds as much solute as is possible at that temperature.
  44. 44. Undissolved solid remains in flask.
  45. 45. Dissolved solute is in dynamic equilibrium with solid solute particles.</li></ul>Degree of Saturation<br />
  46. 46. Degree of Saturation<br /><ul><li>Unsaturated Solution
  47. 47. Less than the maximum amount of solute for that temperature is dissolved in the solvent.
  48. 48. No solid remains in flask.</li></li></ul><li>Degree of Saturation<br /><ul><li>Supersaturated
  49. 49. Solvent holds more solute than is normally possible at that temperature.
  50. 50. These solutions are unstable; crystallization can often be stimulated by adding a “seed crystal” or scratching the side of the flask.</li></li></ul><li>FACTORS AFFECTING<br />SOLUBILITY<br />
  51. 51. Factors Affecting Solubility<br />Chemists use the axiom <br />“like dissolves like”<br /><ul><li>Polar substances tend to dissolve in polar solvents.
  52. 52. Nonpolar substances tend to dissolve in nonpolar solvents.</li></li></ul><li>LABORATORY ACTIVITY 2.8FACTORS SOLUBILITY <br />IMMISCIBLE<br />MISCIBLE<br />MISCIBLE<br />S/MISCIBLE<br />SOLUBLE<br />SOLUBLE<br />INSOLUBLE<br />INSOLUBLE<br />
  53. 53. Temperature<br /> Generally, the solubility of solid solutes in liquid solvents increases with increasing temperature.<br />
  55. 55. Temperature<br /><ul><li>The opposite is true of gases. </li></ul>Higher temperature drives gases out of solution.<br /><ul><li>Carbonated soft drinks are more “bubbly” if stored in the refrigerator.
  56. 56. Warm lakes have less O2 dissolved in them than cool lakes.</li></li></ul><li>Molecular Size<br /><ul><li>The larger the molecules of the solute are, the larger is their molecular weight and their size.
  57. 57. It is more difficult it is for solvent molecules to surround bigger molecules.
  58. 58. If all of the above mentioned factors all excluded, a general rule can be found that larger particles are generally less soluble. 
  59. 59. If the pressure, and temperature are the same than out of two solutes of the same polarity, the one with smaller particles is usually more soluble.</li></li></ul><li>LABORATORY ACTIVITY 2.8FACTORS SOLUBILITY <br />TAKES TIME <br />TO DISSOLVE<br />EASILY<br />DISSOLVED<br />TAKES TIME <br />TO DISSOLVE<br />EASILY<br />DISSOLVED<br />
  60. 60. Effect of Stirring<br /><ul><li>Stirring only increases the speed of the process - it increases the movement of the solvent that exposes solute , thus enabling solubility.
  61. 61. As molecules in liquid substances are in constant move, the process would take place anyway, but it would take more time.</li></li></ul><li>LABORATORY ACTIVITY 2.8FACTORS SOLUBILITY <br />DISSOLVES<br />FASTER<br />TAKES TIME<br />DISSOLVES<br />DISSOLVES<br />FASTER<br />TAKES TIME<br />DISSOLVES<br />
  62. 62. Factors Affecting Solubility<br /> The stronger the intermolecular attractions between solute and solvent, the more likely the solute will dissolve.<br />Example: ethanol in water<br />Ethanol = CH3CH2OH<br />Intermolecular forces = H-bonds; dipole-dipole; dispersion<br />Ions in water also have ion-dipole forces.<br />
  63. 63. Factors Affecting Solubility<br /><ul><li>Glucose </li></ul>(which has hydrogen bonding) is very soluble in water.<br /><ul><li>Cyclohexane</li></ul>(which only has dispersion forces)is not water-soluble.<br />
  64. 64. Factors Affecting Solubility<br />Vitamin A is soluble in nonpolar compounds <br />(like fats).<br />Vitamin C is soluble in water.<br />
  65. 65. Which vitamin is water soluble and which is fat soluble?<br />HEALTHAPPLICATION<br />
  66. 66. Gases in Solution<br />In general, the solubility of gases in water increases with increasing mass.<br />Why?<br />Larger molecules have stronger dispersion forces.<br />
  67. 67. Gases in Solution<br />The solubility of liquids and solids does not change appreciably with pressure.<br />But, the solubility of a gas in a liquid is directly proportional to its pressure.<br />Increasing pressure above solution forces more gas to dissolve.<br />
  68. 68. Henry’s Law<br />States that:<br />
  69. 69. Henry’s Law<br />Sg = kPg<br />Where:<br />Sg is the solubility of the gas;<br />k is the Henry’s law constant for that gas in that solvent;<br />Pgis the partial pressure of the gas above the liquid.<br />