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Solutions

Solutions. Solution Saturation. Compares the amount of dissolved solute in a solution with the maximum amount of dissolved solute possible under the given conditions. UNSATURATED SOLUTION more solute dissolves. SATURATED SOLUTION no more solute dissolves. SUPERSATURATED SOLUTION

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Solutions

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  1. Solutions

  2. Solution Saturation Compares the amount of dissolved solute in a solution with the maximum amount of dissolved solute possible under the given conditions.

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

  4. Solubility • A solution that contains the maximum possible amount of solute is saturated. • If a solution contains less than the maximumamount of solute, it is unsaturated.

  5. Solubility • When a solution is saturated and excess solute is present, the rate of dissolution is equal to the rate of crystallization. • Solubility increases with increasing temperature — a saturated solution that was prepared at a higher temperature contains more dissolved solute than it would contain at a lower temperature, when the solution is cooled, it can become supersaturated.

  6. Hotpack / Coldpack

  7. 200 180 160 140 120 100 80 60 40 20 0 Solubility vs. Temperature KI KNO3 Solubility (g solute / 100 g H2O) NaNO3 Na3PO4 NaCl 20 40 60 80 100 Temperature (oC) Timberlake, Chemistry 7th Edition, page 297

  8. Gas Solubility CH4 2.0 O2 Higher Temperature …Gas is LESS Soluble CO Solubility (mM) 1.0 He 0 10 20 30 40 50 Temperature (oC)

  9. gases solids Solubility vs. Temperature for Solids Solubility Table 140 KI 130 120 NaNO3 110 100 KNO3 90 80 HCl NH4Cl • shows the dependence • of solubility on temperature 70 Solubility (grams of solute/100 g H2O) 60 NH3 KCl 50 40 30 NaCl KClO3 20 10 SO2 0 10 20 30 40 50 60 70 80 90 100 LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 517

  10. Solubility • Solubility • maximum grams of solute that will dissolve in 100 g of solvent at a given temperature – Solubility is expressed as (g/L) or (g/g) or (mol/L). • varies with temperature • based on a saturated solution

  11. Solubility • Solids are more soluble at... • high temperatures. • Gases are more soluble at... • low temperatures & • high pressures (Henry’s Law). • EX: nitrogen narcosis, the “bends,” soda

  12. KNO3 (s) KCl (s) Solubility (g/100 g H2O) HCl (g) Temp. (oC) Solubilityhow much solute dissolves in a given amt. of solvent at a given temp. SOLUBILITY CURVE Unsaturated: solution could hold more solute; belowline saturated: solution has “just right” amt. of solute; on line supersaturated: solution has “too much” solute dissolved in it; abovethe line

  13. Sol. Sol. To To Solids dissolved in liquids Gases dissolved in liquids As To , solubility As To , solubility

  14. Classify as unsaturated, saturated, or supersaturated. 80 g NaNO3 @ 30oC 45 g KCl @ 60oC 50 g NH3 @ 10oC 70 g NH4Cl @ 70oC saturated per 100 g H2O unsaturated unsaturated supersaturated Per 500 g H2O, 120 g KNO3 @ 40oC saturation point @ 40oC for 100 g H2O = 66 g KNO3 So sat. pt. @ 40oC for 500 g H2O = 5 x 66 g = 330 g 120 g < 330 g unsaturated

  15. Solubility of Sodium Acetate 150 Saturated Supersaturated solution Video Clip 100 Solubility(g/100 g H2O) Unsaturated solution 50 0 The small crystal causes extensive crystallization, and eventually A single crystal of sodium acetate, NaC2H3O2, is dropped into a supersatureated solution 25 50 75 100 the solute forms a solid mass of NaC2H3O2. Temperature (oC) Charles H.Corwin, Introductory Chemistry 2005, page 378

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