Solubility Section 8.5. Solubility  When we dissolve a solute in water, there is a point where no...

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Transcript of Solubility Section 8.5. Solubility  When we dissolve a solute in water, there is a point where no...

  • Slide 1
  • Solubility Section 8.5
  • Slide 2
  • Solubility When we dissolve a solute in water, there is a point where no more will dissolve Saturated solution - a solution containing the maximum quantity of a solute at specific temperature and pressure conditions look for the presence of undissolved solids in the solution Solubility the concentration of a saturated solution of a solute at a specific temperature and pressure Units for solubility are usually grams of solute per 100 mL of solvent (g/100mL)
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  • Unsaturated solution = a solution containing less than maximum quantity of a solute at specific temperature and pressure conditions Supersaturated solution = a solution that contains more of the dissolved material than could be dissolved by the solvent under normal circumstances Other Important Terms
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  • Solubility SATURATED SOLUTION no more solute dissolves UNSATURATED SOLUTION more solute dissolves SUPERSATURATED SOLUTION becomes unstable, crystals form increasing concentration
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  • Solubility tables (pg. 324) ionic compounds are listed as having either high or low solubility at SATP (25C and 100 kPa) anions paired with particular cations have either: High solubility OR Low solubility
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  • Solubility Categories High solubility = with a maximum concentration at SATP (standard ambient temperature and pressure) of greater than or equal to 0.1mol/L Low solubility = with a maximum concentration at SATP of less than 0.1mol/L Insoluble = a substance that has a negligible solubility at SATP
  • Slide 7
  • Solubility of Solids Solubility of a solid changes with temperature Higher solubility at higher temperatures in industry, the solute is isolated from many solutions by evaporating the solvent this increases the concentration of a solution and once it is greater than the solubility, the solute crystallizes (precipitates) out Solubility Curve = a graph of solubility versus temperature
  • Slide 8
  • Solubility Curve of Solids (pg. 394) Solubility is most affected by temperature The line shows you how much solute can dissolve in 100g of water at a particular temperature. A concentration on the line is a saturated solution Concentrations above the line are supersaturated Concentrations below the line are unsaturated
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  • What can I do with a solubility curve? Calculating the amount of solute that needs to be added to a solution to make saturate it. Calculating the amount of solute that will crystallize out of solution when the solution is cooled.
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  • per 100 g H 2 O Classify as unsaturated, saturated, or supersaturated. 80 g NaNO 3 @ 30 o Cunsaturated 45 g KCl @ 60 o Csaturated 50 g NH 3 @ 10 o Cunsaturated 70 g NH 4 Cl @ 70 o Csupersaturated So sat. pt. @ 40 o C for 500 g H 2 O = 5 x 66 g = 330 g 120 g < 330 gunsaturated saturation point @ 40 o C for 100 g H 2 O = 66 g KNO 3 Per 500 g H 2 O, 120 g KNO 3 @ 40 o C
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  • (A) Per 100 g H 2 O, 100 g Unsaturated; all solute NaNO 3 @ 50 o C. dissolves; clear solution. (B) Cool solution (A) very Supersaturated; extra slowly to 10 o C. solute remains in solution; still clear. Describe each situation below. (C) Quench solution (A) in Saturated; extra solute an ice bath to 10 o C. (20 g) cant remain in solution, becomes visible.
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  • Solubility of Gases Gases have a higher solubility at lower temperatures Think: Pop glass of cola sitting in the refrigerator as compared to one sitting on the kitchen counter Can of pop is also stored under pressure Increased pressure = increased solubility
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  • Solubility Graph LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World, 1996, page 517 0 10 20 30 40 50 60 70 80 90 100 Solubility vs. Temperature for Solids Solubility (grams of solute/100 g H 2 O) KI KCl 20 10 30 40 50 60 70 80 90 110 120 130 140 100 NaNO 3 KNO 3 HClNH 4 Cl NH 3 NaCl KClO 3 SO 2 shows the dependence of solubility on temperature gases solids
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  • Solubility of Sodium Acetate Temperature ( o C) 0 255075100 Solubility(g/100 g H 2 O) 50 100 150 Supersaturated solution Unsaturated solution Saturated Video Clip Charles H.Corwin, Introductory Chemistry 2005, page 378 A single crystal of sodium acetate, NaC 2 H 3 O 2, is dropped into a supersatureated solution The small crystal causes extensive crystallization, and eventually the solute forms a solid mass of NaC 2 H 3 O 2.
  • Slide 15
  • Homework Worksheet: Solubility Curves & Solubility Tables