Chapter 13.2 : The Solution Process


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Chapter 13.2 : The Solution Process

  1. 1. The solution process<br />Chapter 13.2<br />Objectives :<br />List and explain three factors that affect the rate at which a solid solute dissolves in a liquid solvent.<br />Explain solution equilibrium, and distinguish among saturated, unsaturated, and supersaturated solutions.<br />Explain the meaning of “like dissolves like” in terms of polar and nonpolar substances.<br />List the three interactions that contribute to the heat of solution, and explain what causes dissolution to be exothermic or endothermic.<br />Compare the effects of temperature and pressure on solubility.<br />
  2. 2. Factors Affecting the Rate of Dissolution<br />Increasing the surface area of the solute<br />Sugar cube will dissolve slower than ground up sugar<br />Agitating a solution<br />Stir your iced tea and the sugar<br /> will dissolve faster.<br />Heating a Solvent<br />Sugar dissolves faster in hot tea<br />
  3. 3. Solubility<br />Solution equilibrium<br />Physical state in which the opposing processes of dissolution and crystallization of a solute occur at equal rates.<br />Saturated solution<br />Solution that contains the maximum amount of dissolved solute<br />Example: At 20oC, 35.9 g of NaCl is the maximum amount that will dissolve in 100. g of water<br />Unsaturated solution<br />Solution that contains less solute than a saturated solution under existing conditions<br />
  4. 4. Supersaturated solutions<br />Solution that contains more dissolved solute than a saturated solution contains under the same conditions.<br />Disturbing solution will cause rapid crystallization<br />Video demonstration 1<br />Video demonstration 2<br />Solvent : water<br />Solute : glucose<br />
  5. 5. Solute-Solvent Interactions<br />“Like dissolves Like”<br />Polar will dissolve polar<br />Nonpolar will dissolve nonpolar<br />Polar will NOT dissolve in nonpolar<br />Dissolving ionic compounds in aqueous solutions<br />Hydration : solution process with water as the solvent<br />CuSO4•5H2O - hydrate<br />Crystalline compounds that incorporate water molecules<br />
  6. 6. Nonpolar solvents<br />Carbon tetrachloride and toluene<br />Substances similar to oil<br />Liquid solutes and solvents<br />Immiscible<br />LIQUID solutes and solvents that are not soluble in each other<br />Example: oil and vinegar<br />Miscible<br />Liquids that dissolve freely in one another in any proportions<br />Ethanol and water<br />
  7. 7. Effects of Pressure on Solubility<br />Increase in pressure – increases gas solubilities in liquids<br />gas + solvent solution<br />Henry’s Law<br />Solubility of a gas in a liquid is directly proportional to the partial pressure of that gas on the surface of the liquid.<br />Effervescence<br />Rapid escape of a gas from a liquid in which it is dissolved<br />Mentos demo<br />
  8. 8. Effects of Temperature on Solubility<br />For gaseoussolutes<br />Increase in temperature<br />Decrease in solubility<br />For solid solutes<br />Increase in temperature<br />Increase in solubility<br />
  9. 9. Heats of solution<br />Formation of solution – accompanied by energy change<br />Dissolving KI<br />Feels cold <br />Dissolving LiCl<br />Feels hot<br />Examples of graphing different heats of solutions<br />Solvated : A solute particle that is surrounded by solvent molecules<br /><ul><li>Heat of Solution – net amount of heat energy absorbed or released when a specific amount of solute dissolves</li>