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1. Solvent only  no solute

1. Solvent only  no solute. 2. Add solute and stir until it enters solution :. This is called an unsaturated solution. It holds less than the maximum. Add more solute and stir. Eventually, no more solute will dissolve in. It settles to the bottom of the

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1. Solvent only  no solute

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  1. 1. Solvent only  no solute 2. Add solute and stir until it enters solution: This is called an unsaturated solution. It holds less than the maximum. • Add more solute and stir. Eventually, no more solute • will dissolve in. It settles to the bottom of the • container. You have reached the maximum • amount of solute at a given T. • This solution is saturated.

  2. The difference between saturated and insoluble:

  3. Solubility Curves (Table G): (grams of solute per 100 g H2O) versus temperature T. The curved line plots show the maximum solubility at a given T. The is the amount of solute in solution at saturation. What is the maximum amount KNO3 that can be dissolved in 100 g of water at 20 0C? At 40 0C? At 60 0C?

  4. Let’s look at one curve in more detail: At A, the solution is unsaturated. If there is not a temp change, how much more solute can be added before saturation is reached? At B, the solution is saturated with 55 g of solute. Any additional solute that is added will not dissolve. It will simply settle to the bottom of the container.

  5. If the temperature of this same solution is reduced to 20 0C, the curve says that only 35 g of solute can be dissolved in. This means that 20 g of the 55 g that were in solution must precipitate out, often as tiny crystals of solute. Once this occurs, the solution will be saturated at point C. Sometimes, if the solution is pure and cooled slowly, no crystals precipitate out. You reach point D. There, you have more solute than is present in a saturated solution. It is called supersaturated. Such solutions are unstable. The addition of a single crystal of solute or other impurity will cause the additional solid to form. In this case, the solution will return to its saturated condition, point C.

  6. http://www.youtube.com/watch?v=0wifFbGDv4I http://www.youtube.com/watch?v=HnSg2cl09PI&NR=1 http://www.youtube.com/watch?v=xTIzMaSDZ3k&feature=related http://www.youtube.com/watch?v=w2mj-Sq2oeo&feature=related

  7. Use Table G to answer the following questions : • At 50 0C, which solute is saturated when 58 g are • completely dissolved in 100 g of water? • 2. Is a solution of 80 g of sodium nitrate in 100 g of • water at 40 0C saturated or unsaturated? • Which compound is least soluble in water at 70 0C? • Which is most soluble at that same temp? • 20 g of KCl are dissolved in 100 g of water at 80 0C. • How much more KCl can be dissolved in at that temp? • This solution is carefully cooled to 50 0C, and no KCl • precipitates out, what is the name of such a solution? • A crystal of KCl is put into this solution, and crystals • fall out of solution. How much KCl remains in solution?

  8. Two new terms: Concentrated solutions contain relatively large amounts of solute in a given amount of solvent. Dilute solutions contain relatively small amounts of solute in a given amount of solvent. Do NOT confuse with saturated and unsaturated! For example, 7 g of KClO3 in 100 g H2O at 10 0C is dilute (relatively little solute), but saturated. Likewise, 130 g of KI in 100 g H2O at 10 0C is concentrated (a lot of solute), but unsaturated.

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