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Solutions

Solutions . Solutions . A solution is a homogeneous mixture of 2 or more substances in a single phase. One constituent is usually regarded as the SOLVENT and the others as SOLUTES . Solution. Solvent. Solute. Parts of a Solution.

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Solutions

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  1. Solutions

  2. Solutions A solution is a homogeneous mixture of 2 or more substances in a single phase. One constituent is usually regarded as the SOLVENTand the others as SOLUTES.

  3. Solution Solvent Solute Parts of a Solution • SOLUTE – the part of a solution that is being dissolved (usually the lesser amount) • SOLVENT – the part of a solution that dissolves the solute (usually the greater amount) • Solute + Solvent = Solution

  4. Nature of Solutes in Solutions • Spread evenly throughout the solution • Cannot be separated by filtration • Can be separated by evaporation • Not visible, solution appears transparent • May give a color to the solution

  5. Solutions Examples Gas in a Gas  Air Gas in a Liquid  Soda Liquid in a Liquid  Gasoline Solid in a Liquid  Sea Water Solids in Solids  Brass Non-Examples water salad soil

  6. Water is the universal solvent • because more substances dissolve in water than in any other chemical. • This has to do with the polarity of each water molecule.

  7. H H–C–H H–C–H H–C–H H–C–H H H H O Molecular Polarity Nonpolar molecules: -- e– are shared equally fats and oils e.g., Polar molecules: -- e– NOT shared equally water e.g.,

  8. Water Molecules • Are polar because O is more electronegative than H • Gives O a partial negative charge. • Form strong intermolecular hydrogen bonds. • Water molecules are attracted to one another better than other molecules its size.

  9. Hydrogen bonding animation Hydrogen bonding occurs because of polarity One water molecule bonds to another.

  10. Surface Tension • Because of the hydrogen bonds, water molecules are attracted to each other. • Liquid water acts like it has a skin. • Water forms round drops.

  11. Properties of Water Hydrogen bonding causes: • High surface tension • Low vapor pressure • High specific heat capacity • High heat of vaporization • High boiling point

  12. Properties of Water

  13. What is, or is not, soluble in H20? Like Dissolves Like • “Polar solvents dissolve ionic compounds and polar molecules • Water is polar therefore it can dissolve • NaCl • Copper (II) sulfate • NaOH • Nonpolar solvents dissolve nonpolar compounds • Oil is nonpolar, which is why oil and water separate

  14. Animations of the Solvation(Animation of a Solute Dissolving) While you watch each video clip, record your observations on your notes. Animation of Salt Dissolving in Water Animation of Sugar Dissolving in Water

  15. O H H H H O O H H H H O O H H O O H H H H H H O H O H When Ionic Solids Dissolve Animation

  16. Aqueous Solutions How do we know ions are present in aqueous solutions? The solutions can conduct electricity They are called ELECTROLYTES HCl, MgCl2, and NaCl are strong electrolytes. They dissociate completely (or nearly so) into ions.

  17. Electrolyte vs. Non-Electrolyte Salt (Ionic Solids) Sugar (Molecular Solids) Both Broke apart into ions Broke apart into whole molecules Water is the solvent. Was able to light the light bulb Did not light the light bulb Forms a solution an electrolyte a non-electrolyte Can Conduct an Electric Current Can’t Conduct an Electric Current An electrolyte is a substance when dissolved in water canconduct an electric current. A non-electrolyte is a substance when dissolved in water can’tconduct an electric current.

  18. Rate of Solution = How Fast Exploration • To an empty 250mL beaker, add approximately 100mL of warm-hot water from a hot plate. • To an empty 250mL beaker, add approximately 100mL of ice water. Be sure to leave the ice behind!  • Add a sugar cube to each of the 250mL beakers. Observe what happens. • Record your observations on your notes. • List other ways that you believe that you could make a solute dissolve more quickly.

  19. Electrolytes in the Body • Carry messages to and from the brain as electrical signals • Maintain cellular function with the correct concentrations electrolytes

  20. Rate of Solution What are ways that you make a solute dissolve faster? • Increase the temperature. • Crush or use smaller size solute particles. • Stir the solutions.

  21. Solubility = How Much Pressure has no effect on the solubility of a solid. Solubility generally increases as temperature increases. Solubility generally decreases as temperature increases. Solubility generally increases as pressure increases.

  22. Types of Solutions There are three ways to classify a solution. • Unsaturated Solutions • Saturated Solutions • Supersaturated Solutions

  23. Types of Solutions A solution in which more solute can dissolve Below the Line A solution in which contains the maximum amount of solute On the Line A solution in which contains more than the maximum amount of solute Above the Line

  24. Supersaturated • The solution is holding more solute than it should be able to. This is achieved by heating the solution and then cooling it slowly. • Examples: rock candy, southern style sweet tea, chemical heat packs • Supersaturated solutions are unstable. The supersaturation is only temporary

  25. UNSATURATED SOLUTION more solute dissolves SATURATED SOLUTION no more solute dissolves SUPERSATURATED SOLUTION becomes unstable, crystals form Solubility increasing concentration

  26. Supersaturated

  27. Solubility Curves Solubility indicates the amount of solute that will dissolve in a given amount of solvent at a specific temperature. For this curve, • X-Axis • Temperature • Y-Axis • How Much Solute Dissolves in 100g of Water • Various Lines • Each line represents a different solute.

  28. CO2 Supersaturated Solubility Curves Saturated Unsaturated

  29. per 100 g H2O Using an available solubility curve, classify as unsaturated, saturated, or supersaturated. 80 g NaNO3 @ 30oC unsaturated 45 g KCl @ 60oC saturated 30 g KClO3 @ 30oC supersaturated 70 g Pb(NO3)2 @ 60oC unsaturated

  30. Describe each situation below. (A) Per 100 g H2O, 100 g NaNO3 @ 50oC. unsaturated; all solute dissolves; clear solution. (B) Cool solution (A) very slowly to 10oC. supersaturated; extra solute remains in solution; still clear (C) Quench solution (A) in an ice bath to 10oC. saturated; extra solute (20 g) can’t remain in solution and becomes visible

  31. How to use a solubility graph? A. IDENTIFYING A SUBSTANCE ( given the solubility in g/100 cm3 of water and the temperature) • Look for the intersection of the solubility and temperature.

  32. Using Solubility Curves • How much KNO3 would dissolve in 100g of water at 50oC? • How much NH4Cl would dissolve in 200g of water at 70oC? • At what temperature would 22g of KCl be able to dissolve in 50g of water? • Which is more soluble (has a higher solubility) at 40oC? • NH3 • KClO3 84g 120g 68oC

  33. Learning Check : What substance has a solubility of 90 g/100 cm3 in water at a temperature of 25ºC ?

  34. Learning Check : What substance has a solubility of 200 g/100 cm3 of water at a temperature of 90ºC ?

  35. Look for the temperature or solubility • Locate the solubility curve needed and see for a given temperature, which solubility it lines up with and visa versa.

  36. Learning Check: What is the solubility of potassium nitrate at 80ºC ?

  37. What is the solubility of potassium nitrate at 80ºC ?

  38. Learning Check : At what temperature will sodium nitrate have a solubility of 95 g/100 cm3 ?

  39. Learning Check: At what temperature will sodium nitrate have a solubility of 95 g/100 cm3 ?

  40. Learning Check: At what temperature will potassium iodide have a solubility of 230 g/100 cm3 ?

  41. Learning Check: At what temperature will potassium iodide have a solubility of 130 g/100 cm3 ?

  42. Using Solubility Curves: What is the solubility of sodium chloride at 25ºC in 100 cm3 of water ? From the solubility graph we see that sodium chlorides solubility is 36 g.

  43. SOLUBLE OR INSOLUBLE? • Soluble: • able to be dissolved • Insoluble: • does not dissolve in solution (or water) • Precipitate: • an insoluble solid formed when two solutions are mixed

  44. Double Replacement reactions AB + CD AD + CB NaCl + AgNO3 NaNO3 + AgCl

  45. moles solute ( M ) = Molarity liters of solution Concentration of Solute The amount of solute in a solution is given by its concentration.

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