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Chapter 12 SOLUTIONS

Chapter 12 SOLUTIONS

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Chapter 12 SOLUTIONS

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  1. Chapter 12SOLUTIONS

  2. Chapter 12 • Section 1 – Types of Mixtures • Section 2 – The Solution Process • Section 3 – Concentration of Solutions

  3. 12.1 - Types of Mixtures • Distinguish between electrolytes and nonelectrolytes. • List three different solute-solvent combinations. • Compare the properties of suspensions, colloids, and solutions. • Distinguish between electrolytes and nonelectrolytes.

  4. Definitions • Soluble: capable of being dissolved What is something that is soluble? • Solution: homogeneous mixture of two or more substances in a single phase Review: What is a homogeneous mixture?

  5. Homogeneous vs Heterogeneous

  6. Definitions Cont. • Solvent: substance doing the dissolving • Solute: substance dissolved in solution • Can be any combination of solid, liquid, or gas • A solid solution is called an alloy • Example: brass is zinc and copper

  7. Examples In these examples, the substance with the greater volume is the solvent

  8. Particle Models for Gold and Gold Alloy

  9. Suspensions • Suspension: particles in a solvent are so large they settle out unless the mixture is constantly stirred What is an example of a suspension?

  10. Suspensions

  11. Colloids • Colloid: particles that are intermediate in size between those in solutions and suspensions the particles are small enough to be suspended throughout the solvent by the constant movement of the surrounding molecules • Colloidal particles make up the dispersed phase, and water is the dispersing medium. • Example: mayonnaise

  12. Tyndall Effect • Tydnall Effect: when light is scattered by colloidal particles dispersed in a transparent medium • This is used to distinguish between a solution and a colloid • Remember the Types of Solutions Lab from the beginning of the year?

  13. Colloids

  14. Emulsions a mixture of two or more immiscible (un-blendable) liquids

  15. Solutions, Colloids, and Suspensions

  16. Electrolytes • Electrolyte: a substance that dissolves in water to give a solution that conducts electric current • What would make a good electrolyte – ionic or covalent compounds? Why? • Ionic – the positive and negative ions separate from each other in solution and are free to move making it possible for an electric current to pass through the solution

  17. Nonelectrolyte • Nonelectrolyte: a substance that dissolves in water to give a solution that does not conduct electricity • Neutral solute molecules do not contain mobile charged particles so they do not conduct electric current • Example: sugar

  18. Electrical Conductivity of Solutions

  19. 12.2 - The Solution Process Listand explain three factors that affect the rate at which a solid solute dissolves in a liquid solvent. Explainsolution equilibrium, and distinguish among saturated, unsaturated, and supersaturated solutions. Explainthe meaning of “like dissolves like” in terms of polar and nonpolar substances. Listthe three interactions that contribute to the enthalpy of a solution, and explain how they combine to cause dissolution to be exothermic or endothermic. Comparethe effects of temperature and pressure on solubility.

  20. Dissolving Process Video

  21. Factors Affecting the Rate of Dissolution 1. Increase the surface area -- because dissolution occurs at the surface 2. Stirring or shaking -- increases contact between solvent and solute 3. Increase the temperature -- increases collisions between solute and solvent and are of higher energy

  22. Factors Affecting the Rate of Dissolution

  23. Solubility • If you add spoonful after spoonful of sugar to tea, eventually no more sugar will dissolve. • There is a limit to the amount of solute that can dissolve in a solvent. • The limit depends on: • Solute • Solvent • Temperature

  24. Particles of Soluble Substances

  25. Particles of Insoluble Substances

  26. Solubility Cont. • When a solute is added, the molecules leave the solid surface and move about at random. • As more solute is added, more collisions occur between dissolved solute particles. Some of the solute molecules return to the crystal. • When maximum solubility is reached molecules are returning to the solid form at the same rate they are going into solution (much like the vapor pressure of a liquid) • This is called solution equilibrium

  27. Solution Equilibrium Video

  28. Solutions • Saturated Solution: contains the maximum amount of dissolved solute • Supersaturated Solution: contains more dissolved solute than a saturated solution • Unsaturated Solution: contains less solute than a saturated solution under the same condition

  29. Mass of Solute Added Versus Mass of Solute Dissolved

  30. Solutions Cont. • When a saturated solution is cooled, the excess solute usually comes out of solution, leaving the solution saturated at the lower temperature. • A supersaturated solution will form crystals of solute if disturbed or more solute is added.

  31. Solubility Values • Solubility: the amount of substance required to form a saturated solution with a specific amount of solvent at a specified temperature • Example: solubility of sugar is 204 g per 100 g of water at 20OC • Solubilities vary widely and must be determined experimentally

  32. Solubility of Common Compounds

  33. Solubility of Common Compounds

  34. Saturated Solution and Temperature

  35. Solute-Solvent Interactions • Solubility depends on the compounds involved. • “LIKE DISSOLVES LIKE” is used to predict whether one substance will dissolve in another • What makes substances similar depends on: • Type of bond • Polar/Nonpolar molecules • Intermolecular forces

  36. Like Dissolves Like

  37. Dissolving Ionic Compounds in Aqueous Solutions • What type of forces are present in water? • These forces attract the ions in ionic compounds and surround them, separating them from the crystal surface and drawing them into solution. • Hydration: when water is the solvent • Ions are said to be hydrated

  38. Hydration of Lithium Chloride

  39. Nonpolar Solvents • Ionic compounds are generally not soluble in nonpolar solvents • Example: carbon tetrachloride, CCl4 toluene, C6H5CH3 • The nonpolar solvent does not attract the ions to break apart the forces holding the crystal together. • There are differences in: __________ , ___________ , __________

  40. Liquid Solutes and Solvents • Oil and water do not mix because oil is nonpolar and water is polar. The hydrogen bonding squeezes out whatever oil molecules may come between them. • Two polar substances or two nonpolar substances easily form solutions. • Immiscible: liquids that are not soluble in each other • Miscible: liquids that dissolve freely in one another in proportion

  41. Comparing Miscible and Immiscible Liquids Video

  42. Pressure and Solubility • Increases in pressure, increase gas solubilities in liquids • An equilibrium is established between a gas above a liquid solvent and the gas dissolved in a liquid

  43. Pressure and Solubility Cont. • Increasing the pressure… causes gas particles to collide with the liquid surface and forces more gas into the solution • Decreasing the pressure… allows more dissolved gas to escape from solution

  44. Soda Carbonation Video

  45. Henry’s Law • Henry’s Law: solubility of a gas in a liquid is directly proportional to the partial pressure of that gas on the surface of the liquid • In carbonated beverages, the solubility of carbon dioxide is increased by increasing the pressure. The sealed containers contain CO2 at high pressure, which keeps the CO2 dissolved in the beverage, above the liquid. • When the beverage container is opened, the pressure above the solution is reduced, and CO2 begins to escape from the solution. • Effervescence: the rapid escape of a gas from a liquid

  46. Henry’s Law Video

  47. Effervescence

  48. Temperature and Solubility of Gas • Increasing the temperature… Increases the average kinetic energy and allows more solute to escape the attraction of the solvent and escape to the gas phase • At higher temperatures, equilibrium is reached with fewer gas molecules in solution

  49. Temperature and Solubility of Liquids and Solids • Increasing the temperature… Increases in temperature usually increases the solubility of solids in liquids • The solubility depends on the solid and properties of the solid. • A few solid solutes are actually less soluble at higher temperatures.

  50. Solubility vs. Temperature