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Solubility Rules & Reference Tables

Solubility Rules & Reference Tables. Components of a Solution. Solute : substance being dissolved Ex: Salt, Sugar Solvent: substance doing the dissolving Ex: Water, Hexane. What Dissolves in What?. Solute must form attractions to the solvent. Polars dissolve polars

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Solubility Rules & Reference Tables

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  1. Solubility Rules & Reference Tables

  2. Components of a Solution Solute: substance being dissolved Ex: Salt, Sugar Solvent: substance doing the dissolving Ex: Water, Hexane

  3. What Dissolves in What? Solute must form attractions to the solvent. • Polars dissolve polars • Nonpolars dissolve nonpolars • Polar solvents dissolve most ionic crystals

  4. Solubility: How much solute can be dissolved in a volume of solvent under certain conditions of temp. and pressure.

  5. Using Reference Table G • Shows solubility in grams of solute per 100 grams of water at different temperatures

  6. Saturated Solutions: hold max solute possible at that temp. Table G: Solubility curves show saturation levels at different temps (in 100g of water).

  7. Saturated Solutions are at EQUILIBRIUM. Rate of dissolving = Rate of crystallization

  8. Ex: How many grams of NaNO3 are needed to create a sat. solution in 100g of water at 50 °C? • Go to 50 °C and up to NaNO3 and over. • Answer: 116 grams

  9. Look at The Water!! • Table G is for 100 grams of water. • Amount of water in your problem may be different and you need to adjust you answer.

  10. How many grams of NaNO3 are needed to create a sat. solution in 300g of water at 50 °C? Answer: 116 grams x 3 (three times as much water!) Or you can use a proportion: 116 grams = x grams 100 g H20 300g H20

  11. Unsaturated Solutions: could still hold more solute at that temp. Would fall “below the line” on Table G Ex: 40 g of NaNO3 in 100g water at 50°

  12. Supersaturated Solutions: hold more solute than they should at that temp. Would fall “above the line” on Table G Ex: 140 g of NaNO3 in 100g water at 50°

  13. How do Supersaturated Solutions Form? • Created a saturated solution at a high temp. and slowly let solution cool. • Certain solutes can stay in solution (like sodium acetate).

  14. Supersaturated solutions are unstable. Add just one more “seed crystal” to the solution, all the excess solute will precipitate out quickly. Supersaturated Sodium Acetate solution after seed crystal added

  15. Describe These Solutions Saturated, Unsaturated or Supersaturated? • 100 g NH4Cl at 70° in 100 g water • 10 g SO2 at 10° in 100 g water • 40 g NaCl at 90° in 100 g water

  16. 100 g NH4Cl at 70° in 100 g water Falls above the line (Supersaturated)

  17. 10g SO2 at 10° in 100g water Falls below the line (Unsaturated)

  18. 40g NaCl at 90° in 100g water Falls on the line (Saturated)

  19. Concentrated Solutions: have a lot of solute dissolved in the solvent Ex: Saturated solution of KI at 10° 135 grams in 100 g water = pretty concentrated

  20. Dilute Solutions: only have a little solute dissolved. Ex: Sat. solution of SO2 at 50° 4 grams in 100 g water = relatively dilute

  21. Factors Affecting Solubility

  22. Surface Area More contact between solute/solvent particles the faster it dissolves Crush substance into fine powder to dissolve faster. Use mortar and pestle

  23. Stirring or Agitation: Allows for more solute/solvent contact, and faster dissolving of solids and liquids However, stirring will disturb dissolved gases and cause them to come out of solution.

  24. Temperature of Solvent Higher temperature solvents will dissolve solid solutes faster Why? Solvent particles move faster making contact faster with solute.

  25. Gases dissolve better when the temperature of the solvent is colder. Ex: CO2 gas in hot soda (flat) vs. cold soda (fizzy)

  26. Fish in aquariums need the dissolved oxygen in the water, if the temp gets too high they suffocate

  27. Pressure Effects gas solubility only Why? Increasing pressure on a gas above a liquid causes more gas molecules to be “pushed” into solution.

  28. Amount of Solute already Dissolved The more particles already in solution the less solvent molecules available to dissolve new solute.

  29. Miscible: liquids that dissolve in any proportions (ex: alcohol and water) • Immiscible: liquids that do not dissolve in any proportion (ex: oil and water)

  30. Electrolytes: Conduct electricity when dissolved in water

  31. Why do they Conduct? • Create mobile ions in solution. • The more concentrated the solution the more it conducts Includes: • Soluble Ionic Compounds (ex: NaCl) • Acids (ex: HCl) • Bases (ex: NaOH)

  32. Who Will Conduct? • Which of the following compounds will conduct in solution? • C6H12O6 • LiBr • KOH • CH4 • H2SO4 • NO2

  33. C6H12O6 Will Not (Covalent) • LiBr Will (Ionic) • KOH Will (Base) • CH4 Will Not (Covalent) • H2SO4 Will (Acid) • NO2 Will Not (Covalent)

  34. Reference Table F • Describes which ionic compounds are soluble or insoluble in water.

  35. Why are Some Insoluble? • Certain combinations of ions hold together so strongly that water cannot dissolve them into solution

  36. Precipitates • Precipitates are insoluble ionic compounds formed in double replacement reactions. • Determine which product is the insoluble precipitate by using Table F.

  37. You can separate a precipitate by filtration. • The solid will stay on the paper.

  38. Is this soluble or not? CaCO3 • Carbonate (CO3-2) is insoluble and Ca+2 as a partner is not an exception

  39. Is this soluble or not? NaNO3 • Nitrate (NO3-1) is always soluble, there are not exceptions

  40. Is this soluble or not? Li3PO4 • Phosphate (PO4-3) is insoluble, however, Li+1 is a Group 1 ion so it is an exception and the compound is soluble.

  41. Look out for exceptions! CaSO4 MgSO4 PbCrO4 Li2S NH4OH Soluble or Not?

  42. Insoluble CaSO4 • Soluble MgSO4 • Insoluble PbCrO4 • Soluble Li2S • Soluble NH4OH

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