Copyright© by Houghton Mifflin Company. All rights reserved. Chapter 15 Solutions.

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  • Slide 1
  • Copyright by Houghton Mifflin Company. All rights reserved. Chapter 15 Solutions
  • Slide 2
  • Copyright by Houghton Mifflin Company. All rights reserved.2 Solutions = homogeneous mixture; a mixture in which the components are uniformly intermingled. All parts are the same; completely mixed. Solutions can be solids, liquids, or gases. Solid solution = brass (copper = zinc) Solvent = largest amount of substance present Solutes = other substances in solution Aqueous solutions = water is solvent
  • Slide 3
  • Copyright by Houghton Mifflin Company. All rights reserved.3 Figure 15.7: Steps involved in the preparation of a standard aqueous solution.
  • Slide 4
  • Copyright by Houghton Mifflin Company. All rights reserved.4
  • Slide 5
  • 5 15.1 Solubility of ionic substances What is an ionic substance? A substance containing anions (-) and cations (+) that dissolve in water, separating the ions and thus able to conduct an electric current.
  • Slide 6
  • Copyright by Houghton Mifflin Company. All rights reserved.6 Figure 15.1: Dissolving of solid sodium chloride.
  • Slide 7
  • Copyright by Houghton Mifflin Company. All rights reserved.7 Solid state ions are packed closely together. Each polar water molecule attaches itself to a sodium ion or a chloride ion. What does polar mean? One side positive and one side negative. What part of the water molecule attached to the sodium ions? The oxygen, the negative side.
  • Slide 8
  • Copyright by Houghton Mifflin Company. All rights reserved.8 Figure 15.2: Polar water molecules interacting with positive and negative ions of a salt.
  • Slide 9
  • Copyright by Houghton Mifflin Company. All rights reserved.9 Solubility of Polar substances Polar substances contain a polar bond which makes it able to dissolve in water. Sugar and ethanol are polar substances. They have an O-H bond where the H can bond with the water molecule.
  • Slide 10
  • Copyright by Houghton Mifflin Company. All rights reserved.10 Figure 15.3: The ethanol molecule contains a polar OH bond.
  • Slide 11
  • Copyright by Houghton Mifflin Company. All rights reserved.11 Figure 15.3: The polar water molecule interacts strongly with the polar OH bond in ethanol.
  • Slide 12
  • Copyright by Houghton Mifflin Company. All rights reserved.12 Figure 15.4: Structure of common table sugar.
  • Slide 13
  • Copyright by Houghton Mifflin Company. All rights reserved.13 Substances insoluble in water Petroleum does not dissolve in water. C and H form non polar bonds because C and H have similar electronegativities. Nonpolar bonds are non-compatible with the polar bonds in water. **Like substances dissolve.
  • Slide 14
  • Copyright by Houghton Mifflin Company. All rights reserved.14 Figure 15.5: A molecule typical of those found in petroleum.
  • Slide 15
  • Copyright by Houghton Mifflin Company. All rights reserved.15 Figure 15.6: An oil layer floating on water.
  • Slide 16
  • Copyright by Houghton Mifflin Company. All rights reserved.16 Which substance is soluble and which is insoluble?
  • Slide 17
  • Copyright by Houghton Mifflin Company. All rights reserved.17 15.2 Solution Composition The amount of a substance that will dissolve in a solvent is referred to as its solubility. Many factors affect solubility, such as temperature and, in some cases, pressure. There is a limit as to how much of a given solute will dissolve at a given temperature. A saturated solution is one holding as much solute as is allowed at a stated temperature. Unsaturated = not holding as much as allowed.
  • Slide 18
  • Copyright by Houghton Mifflin Company. All rights reserved.18 Figure 12.3: Comparison of unsaturated and saturated solutions.
  • Slide 19
  • Copyright by Houghton Mifflin Company. All rights reserved.19 Solubility: Saturated Solutions Sometimes it is possible to obtain a supersaturated solution, that is, one that contains more solute than is allowed at a given temperature. Supersaturated solutions are unstable. If a small crystal of the solute is added to a supersaturated solution, the excess immediately crystallizes out.
  • Slide 20
  • Copyright by Houghton Mifflin Company. All rights reserved.20 Figure 12.4: Crystallization begins. Photo courtesy of James Scherer.
  • Slide 21
  • Copyright by Houghton Mifflin Company. All rights reserved.21 Amount of substance can vary. Concentrated = a relatively large amount of solute Dilute = a relatively small amount of solute
  • Slide 22
  • Copyright by Houghton Mifflin Company. All rights reserved.22 15.3 Factors Affecting Rate of Dissolving 1. Surface area the more surface area exposed, the faster the substance is dissolved 2. Stirring exposed new surfaces 3. Temperature molecules move faster thus dissolve faster.
  • Slide 23
  • Copyright by Houghton Mifflin Company. All rights reserved.23 15.4 Solution Composition: Mass Percent The mass percentage of solute is defined as: For example, a 3.5% sodium chloride solution contains 3.5 grams NaCl in 100.0 grams of solution.
  • Slide 24
  • Copyright by Houghton Mifflin Company. All rights reserved.24 15.5 Molarity Easier to use volume instead of mass. Concentration = the amount of solute in a given volume of solution. Concentration = M (Molarity) Standard solution = a solution whose concentration is accurately known.
  • Slide 25
  • Copyright by Houghton Mifflin Company. All rights reserved.25 15.5 Molarity The molarity = the number of moles of solute per volume (liters) of solution. For example, 0.20 mol of ethylene glycol dissolved in enough water to give 2.0 L of solution has a molarity of
  • Slide 26
  • Copyright by Houghton Mifflin Company. All rights reserved.26 Figure 15.8: Process of making 500 mL of a 1.00 M acetic acid solution.
  • Slide 27
  • Copyright by Houghton Mifflin Company. All rights reserved.27 Figure 15.9: A bubble in the interior of liquid water surrounded by solute particles and water molecules.
  • Slide 28
  • Copyright by Houghton Mifflin Company. All rights reserved.28 Figure 15.10: Pure water.
  • Slide 29
  • Copyright by Houghton Mifflin Company. All rights reserved.29 Figure 15.10: Solution (contains solute).

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