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Chemistry B Intro to Mixtures

Chemistry B Intro to Mixtures. © Mr. D. Scott; CHS. Mixtures The Dissolving Process Solutions & Solubility Concentration Working with solutions Solution properties. Matter. Classification of Matter. Pure Substances. Mixtures. Heterogeneous. Homogeneous. Elements. Compounds.

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Chemistry B Intro to Mixtures

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  1. Chemistry B Intro to Mixtures © Mr. D. Scott; CHS • Mixtures • The Dissolving Process • Solutions & Solubility • Concentration • Working with solutions • Solution properties

  2. Matter Classification of Matter Pure Substances Mixtures Heterogeneous Homogeneous Elements Compounds

  3. Granite Rock Pizza Sea Water Types of Mixtures Heterogeneous Homogeneous Coffee Chocolate Chip Cookie

  4. Skim Milk Milk Whole Milk Cream It depends on how closely you look at it. Types of Mixtures Where does it belong? Even though we have “homogenized” milk, if you look at it very closely, you can see that the fat globules, and the whey are not evenly distributed at the molecular level. Heterogeneous Homogeneous

  5. Types of Mixtures Where does it belong? Heterogeneous Homogeneous When substances are evenly mixed at the molecular level, they are called solutions. Solutions are homogenous all the way down to the size of molecules and atoms.

  6. Types of mixtures How can you tell the difference between a solution, a colloid and a suspension? First, try filtering it, then look for the Tyndall effect.

  7. Tyndall effect Tyndall effectis occurring if you project a beam of light through a mixture and see the light beam. This effect distinguishes a solution from colloids and suspensions.

  8. Tyndall effect Some everyday examples of the Tyndall effect

  9. Colloids

  10. A solution is a homogenous mixture of 2 or more substances The solute is(are) the substance(s) present in the smaller amount(s) The solvent is the substance present in the larger amount Gas solute mixed in a gas solvent Salt solute mixed in water solvent Solid solute mixed in a solid solvent Gas solute mixed in water solvent Liquid solute mixed in water solvent

  11. Animation: Why oil & water don’t mix Solubility Oil and vinegar salad dressing separates because oil is not soluble in vinegar (mostly water). What dissolves in what? “Like dissolves in Like” This statement is referring to the polarity of the solute & solvent. Non-polar solvents Dissolve Non-polar solutes Polar solvents Dissolve Polar solutes

  12. “Oil & Water”Immiscible liquids

  13. Immiscibility of Oil & Water The incompatibility of oil & water is used by the petroleum industry to increase the amount of oil extracted from oil wells.

  14. Like Substances Polar and Non-polar Ionic

  15. Dissolution of Solid Solute What are the driving forces which cause solutes to dissolve to form solutions? 1. Molecular solutes dissolve by dipole attractions, H-bonding, or by LDF 2. Ionic solutes dissolve by dipole-ion attractions.

  16. Dissolution of Solid Solute What are the driving forces which cause solutes to dissolve to form solutions? 1. Molecular solutes dissolve by dipole attractions, H-bonding, or by LDF 2. Ionic solutes dissolve by dipole-ion attractions. The ring of water molecules around the solute particle is called a “hydration shell.” The solute particle is “solvated” once it is surrounded with solvent molecules.

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  18. Dissolving at the molecular level Consider the dissolution of NaOH in H2O

  19. 3 Stages of the Solution Process • Separation of Solute • must overcome IMF or ion-ion attractions in solute • requires energy, ENDOTHERMIC ( + DH) • Separation of Solvent • must overcome IMF of solvent particles • requires energy, ENDOTHERMIC (+ DH) • Interaction of Solute & Solvent • attractive bonds form between solute particles and solvent particles • “Solvation” or “Hydration” (where water = solvent) • releases energy, EXOTHERMIC (-DH)

  20. Three types of interactions in the solution process: • solvent-solvent interaction • solute-solute interaction • solvent-solute interaction DHsoln = DH1 + DH2 + DH3

  21. Factors Affecting Solubility 1. Nature of Solute / Solvent. - Like dissolves like (IMF) 2. Temperature - i) Solids/Liquids- Solubility increases with Temperature Increase K.E. increases motion and collision between solute & solvent. ii) gas - Solubility decreases with Temperature Increase K.E. result in gas escaping to atmosphere. 3. Pressure - i) Solids/Liquids - Very little effect Solids and Liquids are already close together, extra pressure will not increase solubility. ii) gas - Solubility increases with Pressure. Increase pressure squeezes gas solute into solvent.

  22. Solubilities of Solids vs Temperature Solubilities of several ionic solid as a function of temperature. MOST salts have greater solubility in hot water. A few salts have negative heat of solution, (exothermic process) and they become less soluble with increasing temperature.

  23. A saturated solution contains the maximum amount of a solute that will dissolve in a given solvent at a specific temperature. An unsaturated solution contains less solute than the solvent has the capacity to dissolve at a specific temperature. A supersaturated solution contains more solute than is present in a saturated solution at a specific temperature. Sodium acetate crystals rapidly form when a seed crystal is added to a supersaturated solution of sodium acetate. crystallization

  24. Temperature and Solubility O2 gas solubility and temperature solubility decreases with increasing temperature Aquatic life is dependent upon the amount of dissolved oxygen (D.O.) available in the water.

  25. Temperature & the Solubility of GasesThe solubility of gases DECREASES at higher temperatures

  26. Henry’s LawThe effect of partial pressure on solubility of gases At pressure of few atmosphere or less, solubility of gas solute follows Henry’s Lawwhich states that the amount of gas dissolved in solution is directly proportional to the amount of it’s pressure above the solution. c = k P c = solubility of the gas (M) k = Henry’s Law Constant P = partial pressure of gas Henry’s Law Constants (25°C), k N2 8.42 •10-7 M/mmHg O2 1.66 •10-6 M/mmHg CO2 4.48•10-5 M/mmHg

  27. Henry’s Law & Soft Drinks • Soft drinks contain “carbonated water” – water with dissolved carbon dioxide gas. • The drinks are bottled with a CO2 pressure greater than 1 atm. • When the bottle is opened, the pressure of CO2 decreases and the solubility of CO2 also decreases, according to Henry’s Law. • Therefore, bubbles of CO2 escape from solution.

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