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Properties of Solutions

Properties of Solutions. 15.2. Solvents and Solutes. An aqueous solution is water that contains dissolved substances. the dissolving medium is the solvent . the dissolved particles are the solute . Solutions. Solutions = homogeneous mixtures

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Properties of Solutions

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  1. Properties of Solutions

  2. 15.2 Solvents and Solutes • An aqueous solution is water that contains dissolved substances. • the dissolving medium is the solvent. • the dissolved particles are the solute.

  3. Solutions • Solutions =homogeneous mixtures • In a solution, the solute is dispersed uniformly throughout the solvent.

  4. 15.2 Why does a solution form? • LIKE DISSOLVES LIKE • Polar solvents (water)dissolve ionic compounds and polar compounds. • Nonpolar solvents (gasoline) dissolve nonpolar compounds.

  5. Vitamin A is soluble in nonpolar compounds (like fats). • Vitamin C is soluble in water.

  6. Which vitamin is water-soluble and which is fat-soluble?

  7. How Does a Solution Form? • There are 3 ways a solution can form • 1. dissociation • 2. dispersion • 3. ionization

  8. Dissociation • The process which an ionic compound separates into its ions as it dissolves is called dissociation • Physical change

  9. Dispersion • When a solid breaks into small pieces and is spread throughout the solvent • Ex: lifesaver on your tongue • Physical change

  10. Ionization of Molecular compounds • The process in which neutral molecules gain or lose electrons is known as ionization • Chemical change

  11. Properties of liquid solutions • Conductivity • Freezing and boiling point

  12. Conductivity • When ionic compounds are dissolved in water they separate into ions and the solution is able to conduct electricity

  13. Freezing Point and Boiling Point • Adding a solute to water can increase the boiling point of the solvent and decrease the freezing point of the solvent

  14. Frozen frogs • What about people?

  15. Heat of Solution • During the formation of a solution, heat is either • Absorbed- endothermic- bonds broken (solute and solvent) • Released – exothermic- bonds formed between solute and solvent

  16. In order for a solution to form attractions between the solute particles and attractions between the solvent particles must be broken- this requires energy- endothermic When the new attraction is formed between the solute and solvent- energy is released- exothermic

  17. 16.1 Solubility • A saturated solution contains the maximum amount of solute for a given quantity of solvent at a given temperature and pressure. • An unsaturated solution contains less solute than a saturated solution at a given temperature and pressure.

  18. Degree of saturation • Unsaturated Solution • Less than the maximum amount of solute for that temperature is dissolved in the solvent. • No solid remains in flask.

  19. Degree of saturation • Supersaturated • Solvent holds more solute than is normally possible at that temperature. • These solutions are unstable; crystallization can often be stimulated by adding a “seed crystal” or scratching the side of the flask.

  20. 16.1 Solution Formation • The compositions of the solvent and the solute determineIF a substance will dissolve. • The factors that determine theRATE which asubstance dissolves are: • stirring (agitation) • temperature • the surface area of the dissolving particles

  21. 16.1 Factors Affecting Rate of Solubility • Temperature • The solubility of most solid substances increases as the temperature of the solvent increases. • The solubilities of most gases are greater in cold water than in hot.

  22. 16.1 Factors Affecting Solubility • Pressure • Changes in pressure have little effect on the solubility of solids and liquids, but pressure strongly influences the solubility of gases. • Gas solubility increases as the partial pressure of the gas above the solution increases.

  23. Gases in Solution • The solubility of liquids and solids does not change appreciably with pressure. • But, the solubility of a gas in a liquid is directly proportional to its pressure. Increasing pressure above solution forces more gas to dissolve.

  24. Factors Affecting the Solubility of Gases • Solubility of most gases decreases as temperature increases • Gases tend to have weak intermolecular forces • Ex: N2 and O2 form weak dipole-induced dipole forces and weak dispersion forces with water • As the kinetic energy of particles within a solution increases the gas particles break free from weak attractions and re-enter the gas phase

  25. Temperature • The opposite is true of gases. Higher temperature drives gases out of solution. • Carbonated soft drinks are more “bubbly” if stored in the refrigerator. • Warm lakes have less O2 dissolved in them than cool lakes.

  26. Temperature Generally, the solubility of solid solutes in liquid solvents increases with increasing temperature.

  27. 16.1 Factors Affecting Solubility

  28. Factors Affecting Solubility of Gases • Real life: • Warm soda goes flat faster than cold soda • Fishing • Thermal pollution • The Bends

  29. 16.1 Solubility • Solubility is often expressed in grams of solute per 100 g of solvent.

  30. Gases in Solution • In general, the solubility of gases in water increases with increasing mass. Why? • Larger molecules have stronger dispersion forces.

  31. Gases in Solution

  32. Concentration of Solutions • Percent by Volume • % by volume – volume of solute x 100 • volume of solution

  33. Concentration of Solutions • Percent by Mass • % by mass = mass of solute x 100 • mass of solution

  34. Concentration of Solutions • Molarity • Molarity = moles of solute • moles of solution

  35. Properties of Acids and Bases

  36. Acid and Bases

  37. Acid and Bases

  38. Acid and Bases

  39. Identifying Acids • Acids – produce hydrogen ions (H+) in solution – also known as hydronium ions H3O+

  40. Properties of Acids • Taste sour • React with metals • Change color in indicators • React with carbonates • Contain H+ ions

  41. Acids React with Active Metals Acids react with active metals to form salts and hydrogen gas: HCl(aq) + Mg(s)→ MgCl2(aq) + H2(g) This is a single-replacement reaction

  42. Acids React with Carbonates and Bicarbonates HCl + NaHCO3 Hydrochloric acid + sodium bicarbonate NaCl + H2O + CO2 salt + water + carbon dioxide An old-time home remedy for relieving an upset stomach

  43. Effects of Acid Rain on Marble(marble is calcium carbonate) George Washington: BEFORE acid rain George Washington: AFTER acid rain

  44. Identifying bases • Bitter taste • Slippery feel • Color changes in indicators • Contain hydroxide ions OH -1

  45. Changing indicator color

  46. the flower color can be determined by the relative acidity of the soil: an acidic soil (pH below 6) will usually produce flower color closer to blue, whereas an alkaline soil (pH above 6) will produce flowers more pink. This is caused by a color change of the flower pigments in the presence of aluminium ions which can be taken up into hyperaccumulating plants.

  47. Neutralization • Acid + base → salt + water • HCl + NaOH → NaCl + H2O • A specific type of double replacement reaction

  48. Proton donors and acceptors • Acids can be defined as proton donors • Bases can be defined as proton acceptors • Ex:

  49. Strengths of Acids and Bases • pH scale – the lower the pH the greater concentration of H+ ions in solution

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