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Solutions Aim: SWBAT identify what solutions are and how they work.

Solutions Aim: SWBAT identify what solutions are and how they work. Ms. Katwaru Chemistry St. Agnes HS. Solution vs. Suspension. Solution – homogeneous mixture dissolving = physical change ( not a chemical change)

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Solutions Aim: SWBAT identify what solutions are and how they work.

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  1. SolutionsAim: SWBAT identify what solutions are and how they work. Ms. Katwaru Chemistry St. Agnes HS

  2. Solution vs. Suspension Solution – homogeneous mixture dissolving = physical change (not a chemical change) Dissolved particles (atoms, ions or molecules) are extremely small and solutions cannot be separated by filtering. Suspension – heterogeneous mixture where some particles settle out upon standing ex. muddy water (clay & silt)

  3. Tyndall Effect Light beam is passed through a liquid containing particles in suspension; these particles scatters the light rays. The path of the light rays through the liquid becomes visible in a suspension, having the appearance of a bright cone in the liquid. Ex. Fog – suspended water droplets TyndallEffect – car headlights in fog - spotlight in smoke or dust

  4. Solutions can be dilute (weak) or more concentrated. Molarity (M) = expression of Concentration M = # moles of solute Liters of Solution If 2.0 moles are dissolved in 4.0 Liters… Molarity = 2.0 moles / 4.0 L = 0.50 M

  5. Na 1x23 = 23g Cl 1x35 = 35g 1 mole = 58 g Making Molar Solutions Fill to Line

  6. Calculate Molarity: Given 450 g NaCl (GFM = 58g) in 3.0 Liter. M = # moles of solute Liters of Solution 1) Find # moles (for numerator). Convert grams to moles using GFM. 2) Solve for Molarity. M =

  7. Aqueous Solutions • Solution - a homogenous mixture mixed molecule by molecule. • Solvent - the “stuff” that does the dissolving; larger amount than solute. • Solute - the “stuff” that is dissolved. • Exist in all phases – most common solid (solute) in liquid (solvent). • Aqueous solution (aq)- a solution with water as the solvent.

  8. Solutions

  9. Polar Water Molecules with Hydrogen Bonds = surface tension. • One water molecule H-bonds to another. • Other H-bonds to water molecules all around.

  10. Dissolution & HydrationWater is a Polar Molecule

  11. Hydration of Ions & Orientation of Polar Water Molecule

  12. Factors Affecting Rate of Solution (Dissolving) (Rate = how much over time) • Amount of Solute and Solvent • closer to max. limit = slower rate • Temperature – higher temp. = faster • Stirring – faster with stirring • Particle Size – smaller = faster

  13. Factors Affecting Solubility (max. amount dissolved) • Nature of Solute and Solvent (“Like dissolves Like”) e.g., Polar solvents dissolve polar solutes. • Temperature • Solids - more soluble @ high Temp. • Gases - less soluble @ high Temp. • Pressure • Gases more soluble @ high Pressure

  14. “Like Dissolves Like” • Polar solvents dissolve polar & ionic solutes. Water (polar) dissolves ionic solids and polar covalent solids. Salts (NaCl, KCl) are ionic & form aqueous solutions. • Non-polar dissolves non-polar. Oil (non-polar) and water (polar) don’t mix = immiscible. • Alcohols – dissolve polar & non-polar solutes; but not ionic solutes. Tinctures – alcohol is solvent.

  15. Solutions

  16. Solubility Curves… show max. limit of solute dissolved for a given temp. and vol. of water.Supersaturated = above lineSaturated = onthe lineUnsaturated = below; under the line Temp.

  17. Solubility Curvesmax. amount dissolved in100g = 100mL of water Supersaturated = above line Saturated = on the line Unsaturated = below; under the line

  18. 1) How much KNO3 will dissolve in 100mL @ 50oC? 2) … in 200mL? 3) If 70g of HCl is dissolved @ 50oC in 100g H2O, is this Supersat., Sat. or Unsat.?

  19. Exceptions: • As temperature rises, the solubility curve of GASES decrease.

  20. Solutions of Ionic Compounds conduct electricity = Electrolytes Electrolytes – ions (charged particles) in solution. NiCl2(aq) + KMnO4(aq)

  21. Electrolytes - to conduct electricity in Liquid Phase, mobile (dissolved) ions are required Greater number (#) ions in solution… = greater electrical conductivity = stronger electrolyte.

  22. 3 Types of Electrolyte Compounds Salts(ionic compounds), acids(H+) & bases(OH-) bright dim dark Solutions CH3COOH C6H12O6 KCl Salts = ionic = metal & non-metal K + (aq) & Cl -(aq) Acetic = weak acid H + & CH3COO - Covalent = no ions

  23. Acids, Bases & Salts Solutions ; Release OH- (aq) Salt (aq)  Metal +(aq) + Non-Metal – (aq)

  24. Colligative Properties Properties that depend on the number of solute particles in solution; not the nature of the particles Best example: Boiling Pt. Elevation Freezing Pt. Depression B.P. 100 C F.P. 0 C

  25. Electrolytes – form ions in solutionKCl (aq) 1 K+1 + 1 Cl –1(1 mole) (2 moles particles)CaCl2(aq)  1 Ca+2 + 2 Cl –1 (1 mole) (3 moles of particles)Nonelectrolytes – exist as dissolved molecules (do not form ions)ex. GlucoseC6H12O6 (aq) (1 mole)

  26. Another Colligative PropertySolute Effect on Vapor PressureVapor Pressure (V.P.)= pressure exerted by a vapor in equilibrium with its liquid (or solid)Volatile – substance has some V.P.Non-Volatile – V.P. = zero

  27. Dissolved particles (solute = gray)occupy/prevent solvent particles from entering vapor phase.

  28. Colligative Properties Summary Greater # particles in solution = Greater effect for… - B.P. Elevation - F.P. Depression - Lower Vapor Press.

  29. Which has the greater # particles …1) NaCl (aq) 2) CaCO3 (aq) 3) KCl (aq) 4) Fe2O3 (aq)Hint: Write a balanced dissociation reaction ___ NaCl (s) ___ Na +1 (aq) + ___ Cl –1 (aq)Coefficients =# moles = # particles (aq)

  30. Which has the greater # particles …1) NaCl (aq) 2) CaCO3 (aq) 3) KCl (aq) 4) Fe2O3 (aq)Hint: Write a balanced dissociation reaction ___ NaCl (s) ___ Na +1 + ___ Cl –1___CaCO3 (s)  ___ Ca +2 + ___ CO3–2___KCl (s)  ___ K +1 + ___ Cl –1___Fe2O3 (s)  ___ Fe +3 + ___O–2

  31. Which has the greater # particles … 1) NaCl (aq) 2) CaCO3 (aq)Total # Moles of 3) KCl (aq) 4) Fe2O3 (aq)Particles; Ions _1_ NaCl (s) 1 Na +1(aq) + 1 Cl –1(aq)2_1_CaCO3 (s)  1 Ca +2 (aq) + 1 CO3–2 (aq)2_1_KCl (s)  1 K +1(aq) + 1 Cl –1(aq)2_1_Fe2O3 (s)  2 Fe +2 (aq) + 3O–2 (aq) 5

  32. Which has the greater Boiling Point (BP), lower Freezing Point (FP) and lower Vapor Pressure?1) NaCl (aq) 2) CaCO3 (aq) 3) KCl (aq) 4) Fe2O3 (aq)Because…__________________________________________________________________________

  33. Which has the greater Boiling Point (BP), lower Freezing Point (FP) and lower Vapor Pressure?1) NaCl (aq) 2) CaCO3 (aq) 3) KCl (aq) 4) Fe2O3 (aq)Because… greatest # moles of particles are formed in solution when it dissolves.Fe2O3 (aq) 2 Fe +3 (aq) + 3O3–2 (aq)5 moles

  34. Vaporization vs. Condensation (opposing phase changes) • Liquid to Gas (evap.) • Open Container • Liquid evaporates completely = unlimited vaporiz. • No significant condensation. Evap.

  35. Physical Equilibrium • Closed Container • Rate of Evap. = Rate of Condensat. • Dynamic Equilibrium between the 2 phases; exchange occurs in both directions equally (no net change). • Water level remains unchanged (no net change).

  36. Physical Equilibrium of Saturated Solution Equilibrium Rate of Precipitation = Rate of Dissolving (equal opposing rates) Sat. Dissolved Particles Solid = Precipitate

  37. What kind of ratio does “percent” mean?For example, if a compound consists of 35% oxygen by mass, what does 35% represent (as a ratio)?

  38. 1) What kind of ratio does “percent” mean? 35 % = 35 100 This is a ratio … X out of 100.

  39. Percent Composition by Mass (Ref. Table T) % Comp. = mass of part x 100 mass of whole Given 20.0 g of solute in 2000. g of solution; Calculate % Comp.

  40. % Comp. = mass of part x 100 mass of whole Given 20.0 g of solute in 2000. g of solution; Calculate % Comp. % Comp. = 20 g solute x 100 = 0.01 x 100 2000 g solution % Comp. = 2 g solute x 100 200 g solution % Comp. = 1 g solute x 100 = 1.00 % 100 g solution

  41. Percent is ratio parts per hundred. % = How many parts out of 100. 2 = 20 = 20 % 10 100 Very small values such as 0.02 % are awkward. Use a smaller ratio, parts per million (ppm). ppm = How many parts out of 1,000,000 .002 = .02 = .02 % 10 100 = 200 = 200 ppm 1,000,000

  42. Parts Per Million (ppm) (Table T)PPM is used for low concen. ppm = grams of solute x 1,000,000 grams of solution Given 0.025 g of solute in 2800. g of solution; Calculate concen. in ppm.

  43. Parts Per Million (ppm) ppm = grams of solute x 1,000,000 grams of solution Given 0.025 g of solute in 2800. g of solution; Calculate concen. in ppm ppm = 0.025 g solute x 1,000,000 2800 g solution = 8.9 ppm

  44. Ref. Table F Not-Soluble Soluble Soluble Not-Soluble

  45. = Single Replacement Ref. J *** Elements higher on Ref. J replace lower elements.

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