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Solutions: Types, Concentration, and Solubility

Learn about different types of solutions, concentration calculations, and factors affecting solubility. Understand the concepts of saturation, solubility, and the formation of solutions.

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Solutions: Types, Concentration, and Solubility

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  1. Chapter 15: Solutions

  2. Solution • Solution – a homogeneous mixture of two or more substances in a single physical state. • Properties of solutions – • The particles are very small (atoms, molecules or ions) • the particles in a solution are evenly distributed or uniformly mixed (a spoonful of lemonade tastes the same as the whole glass)

  3. Parts of solutions • Solute – the thing that gets dissolved • Solvent – the thing that does the dissolving • Soluble – something that can be dissolved (salt and sugar) • Insoluble – a substance that cannot be dissolved (Hg and oil)

  4. Types of solutions • Solid Solutions – alloys – made by melting different metals and then cooling them • Makes material stronger, higher melting points and greater resistance to corrosion • Ex. Dental filling – mercury in silver • Sterling silver – copper in silver • 16 karat gold – gold, copper and silver • Coinage bronze – copper, tin and zinc

  5. Types of solutions • Gaseous solutions – air we breathe. Nitrogen with oxygen in it • If gas molecules mix they become a solution. Anytime gases are near each other they will mix, therefore any gas mixture is a solution.

  6. Types of solutions • Liquid Solutions – MOST COMMON! the solvent and the solution are both liquids. The solute can be a gas, liquid or solid. • Miscible – liquids that can be mixed in any amount (water and ethanol) • Immiscible – liquids that cannot mix in any proportion (oil and water)

  7. Types of solutions • Aqueous solutions – solutions with water as the solvent • 2 types • 1. When ionic compounds dissolve, ions are present and make an Electrolyte. (NaCl) • 2. When molecular compounds dissolve, no ions are present and make a nonelectrolyte. (Sugar)

  8. 15-2 Concentration of Solutions • Concentration – the amount of solute in a given amount of solvent. • Molarity = moles of solute • Liters of solution • What is the Molarity of a NaOH solution if 10.0g of NaOH is dissolved in enough solvent to make 0.100L of solution?

  9. You try it!!! • Find the Molarity of a solution formed by mixing 10.0g of H2SO4 with enough water to make 100.0mL of solution • M = 10.0g H2SO4 x 1 mol H2SO4 = 1.02 mol/L • 0.100L sol 98.1 g H2SO4

  10. Molality = moles of solute • Kg of Solvent • If 18.0g of C6H12O6 is dissolved in 1Kg of water. • 18.0g C6H12O6 x 1mol C6­H12O6 = 0.100 mol C6­H12O6 / 1Kg H2O • 1Kg H2O 180g C6­H12O6

  11. Mole Fraction = moles of component • Total moles of solution • What is the mole fraction of SO2 in a gas containing 128.0g of SO2 dissolved in every 1500.g of CO2

  12. 1st change grams to moles • 128g SO2 x 1 mole SO2 = 1.999 moles SO2 64.04 g SO2 • 1500 g CO2 x 1 mole CO2 = 34.09 moles CO2 • 43.99 g CO2 • XSO2 = moles of SO2 • Total moles of solution • 1.999moles SO2 • (1.999 moles SO2 + 34.09 moles CO2) • = 0.05539

  13. Example. • A gas mixture contains 50.4 g of N2O and 65.2g of O2 what is the mole fraction of N2O? (0.360)

  14. 15-3 The formation of Solutions • How they form • Why does salt dissolve? The particles are attracted to the water. The water attaches itself on the face of NaCl and pulls it apart. Then the water surrounds the ions. • solvation - the interaction between solute and solvent • hydration – when the solvent is water

  15. energy is needed when bonds are broken between the solute and solvent • when the solvent and solute are attracted energy is released. • Cold packs = NH4OH • Hot packs = Na2S2O3

  16. Solubility – the amount of solute that will dissolve in a specific solvent under given conditions. • Depends on… • 1. Nature of solute and solvent – polar compounds dissolve polar compounds. IE “likes dissolve likes” cholesterol is nonpolar and fat is nonpolar • 2. Temperature – As temperature increases, gas particles get more energy and solubility of a gas decreases (better to keep soda cold!)

  17. Solubility of a solid – as temp increases, solubility increases (sugar to iced tea or hot tea) • Pressure – solubility of a gas is increases as the pressure increases because when the pressure is increases, the gas particles hit the solution faster. • Scuba divers – nitrogen is dissolved in your blood because of the extra pressure, if they come up too fast the nitrogen will bubble out of your blood. (bends)

  18. Factors affecting the Rate of Dissolving • surface area – the greater the surface area, the faster the solid can be dissolved. (big ice cubes or little ones) • Stirring – allows the solute to be exposed to all of the solvent not just the top • Temperature – warmer is faster

  19. Saturation – if a solution contains as much solute as can possibly be dissolved under the existing conditions of temperature and pressure • Saturated and concentrated are not the same things. A solution can be saturated with only a little amount of solute.

  20. Unsaturated – a solution that has less than the maximum amount of solute • Supersaturated – contains a greater amount of solute than needed to form a saturated solution. The extra solute will eventually go back into solution. (rock candy)

  21. 15-4 Colligative Properties – depend on the collective effort f the solute properties and not their identity. • 1. Vapor pressure reduction – when a nonvolatile solute is added to a solvent, the solute takes up space at the surface which prevents some of the solvent from leaving. Gases are still returning to the liquid at the same rate. This reduces the vapor pressure of the solution.

  22. 2. Boiling point Elevation – antifreeze is added to a car to make the water not boil. Antifreeze is a nonvolatile substance so it reduces the vapor pressure and increases the boiling point because it takes longer to reach atmospheric pressure • Eq. ∆Tb = Kbm • Where ∆Tb = boiling point elevation • Kb = molal boilin point constant (varies with solvent) • m= molality

  23. Problem. Water with sugar added to it will boil at a higher temperature than pure water. By how much will the boiling point of water be elevated if 100g of C12H22O11 is added to 500 g of water. Kb = 0.52 C/m • Molality = mol solute • Kg solution • = 100. g sucrose x 1 mole sucrose = 0.584mol/kg • 0.500kG H2O 342.3g sucrose • ∆Tb = Kbm = 0.52C/m x 0.584 m = 0.30 C

  24. Freezing Point Depression – the temp at which the vapor pressure of the solid and liquid are the same. If the solute is nonvolatile (rock salt)

  25. Eq. ∆Tf = Kfm • Problem. Calculate the freezing point depression of a solution of 100.g of C12H6O2 in 0.500Kg of water. The Kf is 1.86C/m • Molality = mol solute / Kg solution • 100.g C2H6O2 x 1 mol • 0.500Kg 62.0g • =3.23m • ∆Tf = Kfm = 1.86C/m x 3.23m = 6.01C

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