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Solutions: Review of Basic Terms

Solutions: Review of Basic Terms. Solution : a homogeneous mixture of two or more substances Solute : substance that is dissolved Solvent : substance in which solute is dissolved Aqueous Solutions : water is solvent ( aq ).

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Solutions: Review of Basic Terms

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  1. Solutions:Review of Basic Terms • Solution: a homogeneous mixture of two or more substances • Solute: substance that is dissolved • Solvent: substance in which solute is dissolved • Aqueous Solutions: water is solvent (aq).

  2. Solubility: (see Table G) how much solute that can be dissolved in a certain amount of solvent at a given temperature and pressure. • Saturated solution • Unsaturated solution • Supersaturated solution • Excess solid solute will precipitate out of solution when conditions change • Gases decrease in solubilty with an increase in temp. • Solids and liquids increase in solubility with an increase in temp.

  3. Soluble vs. Insoluble Ionic Salts (Table F) • Indicates if relatively large or small quantity of solute will dissolve in water • If amount is really small, salt is called “insoluble”

  4. Methods of Indicating Concentration • How can you tell how many solute particles are dissolved in solution? https://www.youtube.com/watch?v=AkPEyluicYA

  5. Molarity Indicates how many MOLES of solute are dissolved in a certain liters of solution. Molarity = Moles of solute Liters of solution Ex: A 2M solution (2 “molar”) contains 2 moles of solute per liter of solution Note: The molarity definition is based on the volume of the solution, NOT the volume of water.

  6. Molarity Problem Ex. How many moles of HCl are present in 3.0 L of a 4.0 M solution? M = mol L #mol = given mass GFM 4.0 M = x 3.0 L _____ 1 X = 12 mol

  7. You try it… • A 3.0 M HCl(aq) solution contains a total of (1) 3.0 grams of HCl per liter of water (2) 3.0 grams of HCl per mole of solution (3) 3.0 moles of HCl per liter of solution (4) 3.0 moles of HCl per mole of water

  8. Which sample of HCl(aq) contains the greatest number of moles of solute particles? (1) 1.0 L of 2.0 M HCl(aq) (2) 2.0 L of 2.0 M HCl(aq) (3) 3.0 L of 0.50 M HCl(aq) (4) 4.0 L of 0.50 M HCl(aq)

  9. How many total moles of KNO3 must be dissolved in water to make 1.5 liters of a 2.0 M solution? • 0.50 mol • 2.0 mol • 3.0 mol • 1.3 mo

  10. You may have to find out how many moles of solute you have from the grams given first. # moles = grams solute given gram formula mass Or use this formula if grams are given: Grams solute = L x M x GFM solute

  11. #mol = given mass GFM “molar” Molarity Problem Ex What is the molarity of the solution with 117 g of NaCl dissolved in 500. mL of water? M = mol L x = ________ x = 4.00 mol L x = 4.00 M Or 117g = .5 Liters x M x 58.5g/mol 117 g 2.00 mol x = 58.5 g/mol 0.500 L x = 2.00 mol

  12. #mol = given mass GFM Molarity Problem Ex. How many grams of Ba(OH)2 are needed to prepare 2.0 liters of a 2.510-4 M solution? M = mol L 2.510-4 M = _____ x = 0.00050 mol OR Grams = 2.0 Liters x 2.510-4 M x 171 g/mol x x 0.00050 mol= _________ __________ 1 _________ 1 171 g/mol 2.0 L x = 0.086 g

  13. You try it… • What is the molarity of 1.5 liters of an aqueous solution that contains 52 grams of lithium fluoride, LiF, (gram-formula mass =26 grams/mole)? (1) 1.3 M    (2) 3.0 M(3) 2.0 M    (4) 0.75 M

  14. You try it… • What is the Molarity of a solution containing 20 grams of NaOH in 500 milliliters of solution? (1) 1 M      (2) 0.04 M(3) 2 M      (4) 0.5 M

  15. Molarity and Dilution • Problems deal with adding or removing water from a solution and determining the new molarity. • Remember the #moles of solute particles doesn’t change! Initial Final M1 x V1 = M2 x V2 2:30 min with problem https://www.youtube.com/watch?v=QYK3Aj-IUIs

  16. Dilution Examples • Ex: If 500 ml of a 2M solution of glucose is diluted with 1000ml of water, what is the new molarity of the solution? • Ex: If 250ml of a 1.2M solution is heated and 100ml of water evaporates off, what is new concentration?

  17. Parts Per Million • Parts per Million (ppm) is the ratio of the number of grams of solute for every one million grams of solution . Remember: Grams “Solution” = Grams Solute + Grams Solvent 1 ml of H2O = 1 gram https://www.youtube.com/watch?v=aa-m8a-jZ0k https://www.youtube.com/watch?v=ikGLNs3nYlc

  18. Parts per Million Example Ex. What is the ppm of NaCl in the solution with 117 g of NaCl dissolved in 500. mL of water? ppm = g solute x 1000000 g sol’n x = ______ x 1000000 117 g 617 g x = 190000 ppm

  19. Parts per Million Example Ex. What is the number of ppm of C2H4(OH)2 in the solution with 55.5 g (50.0 mL) of liquid C2H4(OH)2 dissolved in 150.0 mL of water ? ppm = g solute x 1000000 g sol’n x = __________ x 1000000 55.5 g 205.5 g x = 270000 ppm

  20. You try it… • An aqueous solution has 0.0070 gram of oxygen dissolved in 1000. grams of water. Calculate the dissolved oxygen concentration of this solution in parts per million.

  21. You try it… • If 0.025 gram of Pb(NO3)2 is dissolved in 100. grams of H2O, what is the concentration of the resulting solution, in parts per million? (1) 2.5 × 10–4 ppm    (2) 2.5 ppm      (3) 250 ppm     (4) 4.0 × 103 ppm

  22. You try it… • What is the total mass of solute in 1000. grams of a solution having a concentration of 5 parts per million? (1) 0.005 g    (2) 0.05 g   (3) 0.5 g    (4) 5 g

  23. Percent Solution • Same idea as parts per milliion, • But instead think of “parts” solute in 100 parts solution. % Solution = grams solute x 100 grams solution

  24. Percent Solution Problems Ex: What is the % solution if 5g glucose is dissolved in 100g water? Ex: If you 500g have a 2% salt solution how many grams of solute does it contain? Ex: If you have a 15% salt solution, how many ppm is the solution?

  25. Conductivity of Solutions • If mobile ions are present in solution the solution will conduct electricity. • Ex: NaCl (aq) • The greater the concentration of these ions, the more it will conduct • Substances that break apart readily to form ions in solution are called strong electrolytes

  26. - - - - + + + + + + + ― ― ― Electrolyte dissolved in Water Nonelectrolyte dissolved in Water Electrolytes & Nonelectrolytes ELECTROLYTES: conduct in solution. • Ex: Soluble ionic compounds and “strong” acids and bases NONELECTROLYTES: do not conduct in solution. • Organic compounds are usually nonelectrolytes. • Ex: Sugars and alcohols Electrolytes provide free moving IONS to water whereas nonelectrolytes do not provide free moving IONS to water.

  27. Electrolytes & Nonelectrolytes Ex.3) Classify the each following solute formulas as a(n) acid, base, salt, sugar, or alcohol and then tell # of particles it would break into if electrolyte (a) KCl ________ # = _____ (b) HCl ________ # = _____ (c) Ba(OH)2 ________ # = _____ (d) CH3OH ________ # = _____ (e) C6H12O6 ________ # = _____ (f) H2SO4 ________ # = _____ (g) CH3COOH ________ # = _____

  28. Dissolving Equations Write the dissolving equations for these substances (a) _______________________________________ (b) _______________________________________ (c) _______________________________________ (d) _______________________________________ (e) _______________________________________ (f) ______________________________________ (g) _______________________________________ H2O KCl(s) H2O HCl(g) H2O Ba(OH)2(s) H2O CH3OH(l) H2O C6H12O6(s) H2O H2SO4(s) H2O CH3COOH(s)

  29. Electrolytes & Nonelectrolytes • Generally (organic / inorganic) _________. substances are nonelectrolytes. • Pure water is a _____________ of electricity. • Ionic compounds do not conduct an electric current when in the __________ phase.

  30. Formation of free moving charged particles as a solute dissolves in water permits the solution to _________ an electric current . • Substances that do not conduct an electric current when dissolved in water are called _______________. • Which of the following substances will conduct electricity the least when added to water? (1) C2H5COOH (3) C6H12O6 (2) Ca(OH)2 (4) ZnSO4

  31. Colligative Properties of Solutions • Have to do with the concentration of particles of solute dissolved in solvent. • Colligative means “of the collection” • When any solutegets dissolved in a solvent three things occur: • Vapor Pressure is Reduced • Boiling Point is Elevated • Freezing Point is Depressed

  32. Vapor Pressure Reduction • Fewer solvent particles are at the solutions surface so less evaporates • Due to solute/solvent attractions, less solvent is able to escape from liquid phase to become vapor. This results in a decrease in vapor pressure.

  33. Boiling Point Elevation All pure liquids have a normal boiling point. Boiling occurs when: Vapor pressure = atm. pressure When solute gets dissolved, VP is reduced and a solution needs to reach a higher temp. before VP = atm. pressure The HIGHER the concentration, the higher the BP will be.

  34. Example: Radiator Coolant • Coolant is added to the water in a car’s radiator which raises the water’s boiling point.

  35. Freezing Point Depression • All pure liquids have a normal freezing point. • Solute particles make it harder for liquid solvent toform a crystalline lattice as a solid. • It requires a lower temp. to freeze • The higher the concentration of solute particles, the lower the freezing point will be. https://www.youtube.com/watch?v=TBkNstDmtj0

  36. Freezing Point Depression

  37. Example: Salt on Sidewalks • Rock salt or super melt are sprinkled on icy sidewalks which lowers the ice’s freezing point. How does salt melt ice? https://www.youtube.com/watch?v=JkhWV2uaHaA

  38. Ex: Making Ice Cream • When making ice cream, salt is added to the ice surrounding the canister. The added salt lowers the ice’s freezing point making the canister colder than 0oC!

  39. Ex: Plane De-Icer, Liquor in Freezer • Airplane’s are de-iced with ethylene glycol. • Vodka or Gin in freezer stays liquid.

  40. Dissociation & Colligative Properties DISSOCIATION FACTOR: Ask yourself: Does solute break apart in solution? IONICS (electrolytes): “Dissociate” in solution • Electrolyte’s colligative effect is greater because it is multiplied by the # of particles it dissociates into in solution COVALENTS (nonelectrolytes): DO NOT dissociate

  41. Dissociation and Colligative Properties • This will effect COLLIGATIVE PROPERTIES • REMEMBER: the more total particles in solution, the greater the colligative “effect”. • A mole of an electrolyte (like a salt) in water would have a greater affect on BP/VP/FP than a mole of a nonelectrolyte • It breaks apart in solution making more particles!!

  42. C6H12O6 C6H12O6 C6H12O6 C6H12O6 C6H12O6 C6H12O6 C6H12O6 C6H12O6 H H H H H H H H H H H H H H H H H H H H H H O O O O O O H H H H H H O O O O O O O O O O O O O O O O H H H H H H O O O O O O H H H H H H H H H H H H H H H H H H H H H H Nonelectrolyte in Solution • Glucose is a sugar which is a nonelectrolyte. • When dissolved in water, glucose does NOT form ions. • Thus a 1.00 mole of glucose dissolved in water will have 1.00 mole of dissolved particles. C6H12O6(s) C6H12O6(aq)

  43. Na+ Cl- Na+ Cl- Cl- Na+ Na+ Na+Cl-Na+Cl- Cl-Na+Cl-Na+ Cl- H H H H H H H H H H H H H H H H H H H H H O O O O O H H H H H H H O O O O O O O O O O O O O O O O H H H H H O O O O O O O H H H H H H H H H H H H H H H H H H H H H H H Electrolyte in Solution • Sodium chloride is a salt which is an electrolyte. • When dissolved in water, sodium chloride does form ions. • Thus a 1.00 mole of sodium chloride dissolved in water will have 2.00 moles of dissolved particles. NaCl(s)Na+(aq) + Cl-(aq)

  44. C6H12O6 Na+ Cl- Na+ C6H12O6 Cl- Cl- C6H12O6 Na+ Na+ C6H12O6 Cl- H H H H H H H H H H H H H H H H H H H H H O O O O O H H H H H H H O O O O O O O O O O O O O O O O H H H H H O O O O O O O H H H H H H H H H H H H H H H H H H H H H H H More Particles = More Effect! • Which of the following two solutions has more dissolved particles? • Which of the following two solutions will have a lower freezing point? 4.0 M C6H12O6 4.0 M NaCl

  45. So How Do I Know If More Particles Again? • Solution has a higher concentration value • Ex: 1M NaClvs 2M NaCl • Ionics make more particles than covalents • Ex: 1M C6H12O6vs 1M KBr • Some ionics make more particles than others • Ex: 2M KClvs 2M CaCl2

  46. Colligative Properties of Solutions Pure water will boil at a _____________ temperature than saltwater. Pure water will freeze at a _____________ temperature than saltwater. Which 1.0 M aqueous solution would have the lowest freezing point? (1) NaCl (2) HCl (3) KCl (4) CaCl2.

  47. If “antifreeze” (ethylene glycol C2H4(OH)2 ) is dissolved in water, then the resulting solution will freeze at a _______________ temp. than normal. If “antifreeze (ethylene glycol C2H4(OH)2 ) is dissolved in water, then the resulting solution will boil at a _______________ temp. than normal.

  48. You Try It… • Compared to pure water, an aqueous solution of calcium chloride has a (1) higher BP and higher FP(2) higher BP and lower FP(3) lower BP and higher FP(4) lower BP and lower FP

  49. You Try It… • Compared to a 2.0 M aqueous solution of NaCl at 1 atmosphere, a 3.0 M aqueous solution of NaCl at 1 atmosphere has a (1) lower boiling point and a higher freezing point(2) lower boiling point and a lower freezing point(3) higher boiling point and a higher freezing point(4) higher boiling point and a lower freezing point

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