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Solutions

Solutions. Solution. Solute. Solvent. Definitions. Solution Homogeneous mixture where particles are uniformly distributed throughout. Solute The substance that dissolves in a solvent Solvent The substance in which a solute dissolves. Definitions.

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Solutions

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  1. Solutions

  2. Solution Solute Solvent

  3. Definitions • Solution • Homogeneous mixture where particles are uniformly distributed throughout. • Solute • The substance that dissolves in a solvent • Solvent • The substance in which a solute dissolves

  4. Definitions • Homogeneous mixture: A mixture that is uniform throughout (that it is uniform at all macroscopic levels and methods of observation.

  5. Solutions • When water is a solvent, the solution is aqueous. • Solvents may be gases: air is a solution of nitrogen, oxygen, argon, and other gases. • Steel is an alloy, solution of one solid dissolved in another solid are solutions of various metals.

  6. Definitions • Solubility • The maximum amount of solute that dissolves in a fixed quantity of a particular solvent (Saturated solution) • Soluble • Capable of being dissolved. • Salt is soluble in water

  7. Solubility Terms • Miscible • Two liquids that are soluble in each other. • If they are soluble in any proportion, they are said to be completely miscible. • Liquids that are partially soluble are said to be partially miscible • Immiscible • Liquids that are not soluble when mixed.

  8. Solubility Terms • Insoluble. When a substance does not appear to dissolve in a solvent. • A concentrated solution has a relatively large amount of solute for given quantity of solution. • A dilute solution has a smaller amount of solute for a given quantity of solution.

  9. Oil is Not Soluble in Water Insert figure 14.4

  10. Solubility • Water will dissolve many compounds • When a compound dissolves in water: • 1. The forces holding “molecules” together are broken. • 2. The forces holding some of the water molecules together are broken. • 3. “Molecules” must interact with the solvent molecules to form attractive forces.

  11. Solubility DISOLVING is different from MELTING DISOLVING is NOT a CHANGE OF STATE

  12. Na Cl Dissolving process in water “Winning IMF”

  13. Na Cl IMF’s IN A SOLUTION IMF: Water – “molecule” IMF: Water - Water IMF: Water – “molecule” IMF: “molecules” in the solid

  14. Effects of Temperature on Solubility 14

  15. Exercises 1. -What’s the solubility of potassium nitrate at 65º C? 2.- What substances have the same solubility at 50ºC? 3.- At what temperature 100g of water will completely disolve 60 g of potassium nitrate ? 4.- What will happen if the previous solution is cooled down to 20ºC? 5.- What is the most soluble substance at 80º? 6.- The solubility of sodium chloride and potassium nitrate is the same at about _____ º C

  16. Exercises 7.- 100 g of water must be at a temperature of ________ ºC to dissolve 100 g of potasium nitrate 8.- 100 g of water must be at a temperature of ________ ºC to dissolve 100 g of lead nitrate 9.- Calculate the mass of potassium nitrate in 200 grams of a saturated solution of potassium nitrate. 10.- Do we have a saturated solution if we dissolve 20 grams of sodium chloride in 100 grams of water at 100 ºC? Why?

  17. Exercises 11.- NH3 (ammonia) and HClare gases. Look for theirsolubilitycurves in thegraph. What’s thedifferencebetweensolubility of solids and gases in water?

  18. Concentration • The concentration of a solution is the amount of solute dissolved in a certain quantity of solvent. • One measure of concentration is . • g/L = mass of solute (g) / L (solution)

  19. Example • Calculate the concentration of a solution made dissolving 10 grams of salt in water. • The volume of the solution is 200 ml • Remember 1 L = 1000 ml • g/L = 10 g salt / 0,2 L solution • Concentration = 50 g/L

  20. Percent by Volume [%(v/v)] • Percent by Volume = • [(volume solute)/(volume solution)]x100% • Calculate the percent by volume alcohol prepared by mixing 15.0 mL with enough water to make a total volume of 50.0 mL. Percent by volume = [(15 mL)/(50 mL)] x 100 = 30%(v/v)

  21. Percent by mass [%(w/w)] • Percent by mass = [(mass solute)/(total mass of solution)]x100% =[(g solute)/(g solute + g solvent)] x 100% How many g of NaCl are required to prepare 100 g of a 5.0% solution? Mass solute = (percent/100)x(total mass) = (5/100)x100 g = 5.0 g NaCl 100g →100% x → 5%

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