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Solutions

Solutions. Define SOLUTION in your own words. ( Please write it down ). Physically Combined. Chemically Combined.  Concentration. Salt water NaOH (aq) HCl (aq). Soup Fruit Cocktail Dirt/Sand. Oxygen Copper Magnesium. Water CaCO 3 CO 2. Solutions. Solutions.

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Solutions

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  1. Solutions Define SOLUTION in your own words. (Please write it down)

  2. Physically Combined Chemically Combined Concentration Salt water NaOH (aq) HCl (aq) Soup Fruit Cocktail Dirt/Sand Oxygen Copper Magnesium Water CaCO3 CO2 Solutions

  3. Solutions SOLUTION - homogeneous mixtures of two or more pure substances. In a solution, the solute is dispersed uniformly throughout the solvent. • SOLUTE– the part of a solution that is being dissolved • (usually the lesser amount) (table salt) • SOLVENT – the part of a solution that dissolves the solute • (usually the greater amount) (water) Solute + Solvent = Solution

  4. Which of the following are Solutions? Muddy Water Orange Juice Blood Milk } } } Gatorade Antifreeze Gasoline Tap Water

  5. Do NOT Copy Blood Milk Muddy Water Orange Juice Cola Antifreeze Gasoline Tap Water

  6. Tyndall Effect Just for your information

  7. SOLUTIONS • Spread evenly throughout the solution - Homogeneous • Cannot be separated by filtration • Can be separated by evaporation • Particles NOT visible (solution appears transparent) • May give a color to the solution Water is the Universal Solvent. Water is the solvent in the production of most of the solutions we use.

  8. Solutions - Revisited • Solutions - homogeneous mixtures of two or more pure substances. • In a solution, the solute is dispersed uniformly throughout the solvent. Greater Lesser HCl(aq) But, how is a solution Formed?

  9. Let us begin by looking at Water Na+ Cl- Charge of +1 Charge of -1 Partial Positive Partial Negative (Lower case delta) Types of Charge Partial Negative Polar Partial Positive Electronegativity of atoms H & O Hydrogen Bond: The IM force of attraction between the polar water molecules

  10. Lets look at Ethanol (C2H5OH) Also Polar Also H-Bond Both PolarBoth H-Bond Like Dissolves Like (Polar dissolves Polar) Before Mixing = separated

  11. Ethanol (C2H5OH) & Water Hydrogen Bonds Break & Reform Ethanol  Water  Like Dissolves Like Before Mixing = separated

  12. Pentane (C5H12) & Hexane (C6H14) Non-Polar Like Dissolves Like Non-Polar dissolves Non-Polar

  13. Inter Molecular Forces H-Bonds LDF

  14. Inter Molecular Forces  LDF  What IM forces would cause hexane and water to mix?  H-Bonds   Polar  But, can they be forced to mix due to greater collisions (higher temp)?

  15. Competing Forces of Attraction in Ionic Compounds Which is stronger? a) H-Bonds between water molecules b) Ionic Bonds between ions

  16. Water: A Polar Molecule Is there a force of attraction between the water molecule and the Cation?

  17. Competing Forces of Attraction Na+ Na+ Cl- Where is there a greater force of attraction? a) Between the Na+ and the water b) Between the Na+ and the Cl- c) The forces are equal -Solvated Ion -Hydration Shell http://www.northland.cc.mn.us/biology/Biology1111/animations/dissolve.html http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/thermochem/solutionSalt.html

  18. Solvation – when an ion (the solute) is surrounded by a solvent. Solvated Ions Hydrated Ions If water is the solvent Hydration Shells are formed when the water molecules (the solvent) surround each ion (the solute)

  19. How Does a Solution Form?What happens when a solid dissolves in a solvent to form a solution? Solvent molecules are attracted to surface ions (attraction is due to opposite charge).

  20. How Does a Solution Form?What happens when a solid dissolves in a solvent to form a solution? 2. Collisions cause surface ions to break free from the crystal lattice.

  21. How Does a Solution Form?What happens when a solid dissolves in a solvent to form a solution? 3. Free ions are surrounded by solvent molecules. The ion becomes solvated. Hydrated: if water is the solvent. This forms a hydration shell

  22. How Does a Solution Form?What happens when a solid dissolves in a solvent to form a solution? 4. The charged ions are stabilized by the hydration shells (decreasing the forces of attraction between the oppositely charged ions). 5. Hydration shells (the solvent) therefore, obstruct reformation of ionic solid.

  23. How Does a Solution Form?What happens when an “IONIC” solid dissolves in a solvent to form a solution? Collisions cause surface ions of the solute to break free from the crystal lattice. Solvent molecules are attracted (IMF) to surface ions of the solute. These free ions are surrounded (IMF) by solvent molecules becoming solvated (hydrated). This decreases the force of attraction between the particles of the solute. Once free & separated, the solute has just been dissolved by the solvent. Watch the cool Animation http://preparatorychemistry.com/Bishop_Solubility_frames.htm

  24. Compounds: Ionic VS. Covalent Covalent - Molecule (Sucrose) Ionic - Crystal Lattice (NaCl) Dissociates Dissolves Dissociates, isn’t that a new term? YES, but we will discuss this in a moment

  25. Covalent Compounds NO - Only intermolecular forces are being broken. The sugar molecule is not altered. (NO Ions created) Like dissolves like Sucrose Water NO Ions created NO Ions created Polar Polar NO Ions created NO Ions created Are any covalent bonds broken when sucrose dissolves?

  26. Ionic Compounds Polar Ionic Bond Ions created Ionic bonds are being broken and ions are dissociating(Floating away into the solution) There is that word again  http://web.mst.edu/~gbert/ANIMATED/Asoly.HTML

  27. Covalent Compounds Dissolve into molecules Ionic Compounds Dissociate into Ions Review is over, lets slow down a little bit and take some notes Dissociated Ions Dissociation: Ionic Bonds are broken Free Ions Dissolving: IM Forces are broken Free Molecules DISSOCIATION: A process using energy to separate a compound into ions (due to solvent)

  28. Saturation Levels Saturated? Unsaturated A saturated solution contains the maximum quantity of solute that dissolves at that temperature. Saturated

  29. Unsaturated Solution Solvent holds less than the maximum amount of solute for that temperature. No solid remains in flask. • Saturated solution • Solvent holds as much solute as is possible (maximum) at that temperature. • Undissolved solid remains in flask. (maybe?) Lets discuss first… then take some notes

  30. Saturation vs. Solubility Unsaturated Saturated The solute dissolved – Less than maximum The solute dissolved – At maximum 1) Will the solute dissolve? (soluble or insoluble) 2) If the solute does dissolve, then how much is the maximum amount of solute dissolved in the solvent? (how much  usuallyMolarity) Solubility

  31. How can we determine the solubility of NaCl? 36.0 g NaCl per 100 g H20 Is this ALWAYS true? There are three factors which influence solubility (how much)? -Temperature -Pressure (gases only) -Solvent Type vs. Solute Type Examples Please NaCl(s)  Na+(aq) + Cl-(aq)

  32. Solvent type vs. Solute type Affects Solubility solute solvent Non-Polar Polar Ethanol Polar moles/100 g solvent Less Polar The stronger the intermolecular attraction between solvent and solute, the higher the solubility (more dissolved solute)

  33. The effect of PRESSURE on the solubility of a gas Think of a soda can before and after it is opened Higher Pressure = Higher Solubility = More solute (gas) dissolved in solvent

  34. Temperature influences solubility (solids) 36.0 g NaCl per 100 mL H20 at 25 °C TEMP & SOLIDS Generally, the solubility of solid solutes in liquid solvents increases with increasing temperature. HIGHER Temp = HIGHER Solubility * 211.3 g sucrose per 100 mL H20 at 25 °C

  35. Temperature influences solubility (Gases) Higher Temp More collisions  Lower Solubility (for gases) • 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.

  36. C12H22O11 (s) + H2O (l) C12H22O11(aq) Sucrose into water: Dissociated Lets Recap Dissolved Ionic Bonds are broken IM Forces are broken NaCl into water: Ions formed NaCl (s) + H2O (l) Na+(aq) + Cl- (aq) REACTED Mg(s) + HCl(aq) • Dissociation & dissolving are a physical changes - you can get back the original solute by evaporating the solvent. • If you can’t, the substance didn’t dissolve, it reacted. A reaction is a chemical change (new substance) Dissolved or Dissociated?

  37. Some Ionic Compounds are Insoluble in Water Solubility or Insolubility in water is determined by the relative forces between species NaCl Dissociates in water (solvent)

  38. Solubility Tables ALWAYS - No Exceptions Ag, Hg, Pb Solubility in WATER

  39. Pb(NO3)2 + NH4Cl  NH4 (NO3) + PbCl2 Pb(NO3)2 NH4Cl NH4 (NO3) PbCl2 (Solid)

  40. KI + Na2CO3 NaI + K2CO3 KI Na2CO3 NaI K2CO3 No Reaction (NR)

  41. KI + CuCl2 KCl + CuI2 KI CuCl2 KCl Cul2 Does NOT Exist Note: CuI2 will decompose: 2 CuI2 → 2 CuI + I2 = (brown precipitate)

  42. Which is the most concentrated? Solute Solvent Strong Weak

  43. Units of Concentration What kind of concentration units have we used in the past? 9 Dots Per Box 38 Dots Per Box 22 Dots Per Box

  44. mass of A in solution total mass of solution 10.0 g NaCl 10.0 g NaCl 9.09 % 10.0 %  100 =  100 = Mass % = Mass % = 10.0 g NaCl + 100.0 g water 100.0 g water Mass Percentage  100 Mass % of A = 10.0 g NaCl into 100.0 g water

  45. mass of A in solution total mass of solution Find the mass percent of 12.72 g AgNO3 dissolved in 40.0 ml water.  100 Mass % of A =

  46. mass of A in solution total mass of solution mass of A in solution total mass of solution mass of A in solution total mass of solution Parts per Million andParts per Billion Parts per Million (ppm) ppm =  106 Parts per Billion (ppb)  109 ppb =  100 Mass % of A =

  47. mol of solute L of solution mol of solute L of solution M = Molarity (M) Capital “M” What is the molarity of 10.0 g NaCladded into 100.0 g water? MM of NaCl = 58.44 g/mol Nacl 1 L 1 mol NaCl 10.0 g NaCl x = 0.171 moles NaCl 58.44 gNaCl 1000 mL 100.0 g water = 100.0 mL water 100.0 mL x = 0.1000 L of solution 0.171 moles NaCl M = 1.71 M = = 0.1000 L solution

  48. Find the molarity of 12.72 g AgNO3 dissolved in 40.0 ml water. mol of solute L of solution mol of solute L of solution M = MM of AgNO3 = 169.88 g/mol AgNO3 40.0 mL = 0.0400 L Water (solvent) = 0.074876 moles AgNO3 12.72 g AgNO3 x 1 mol NaCl 169.88 AgNO3 0.074876 moles AgNO3 M = = 1.87 M = 0.0400 L solution

  49. Molarity (M) mol of solute L of solution M = Molality (m) Lower Case (m) mol of solute kg of solvent m = But, neither moles nor mass change with temperature, molality (unlike molarity) is not temperature dependent. • Volume (L) is temperature dependent, therefore molarity can change with temperature. NOTE: We will not be doing any calculations using molality (m) 

  50. Mass/Mass Moles/Mass Moles/L

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