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Section 15.1 Forming Solutions 1.To understand the process of dissolving 2.To learn why certain substances dissolve in water 3.To learn qualitative terms describing the concentration of a solution 4.To understand the factors that affect the rate at which a solid dissolves Objectives
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Section 15.1 Forming Solutions What is a solution? Solution – homogeneous mixture –Solvent – substance present in largest amount –Solutes – other substances in the solution –Aqueous solution – solution with water as the solvent
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Section 15.1 Forming Solutions
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Section 15.1 Forming Solutions A. Solubility Solubility of Ionic Substances Ionic substances breakup into individual cations and anions.
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Section 15.1 Forming Solutions A. Solubility Solubility of Ionic Substances Polar water molecules interact with the positive and negative ions of a salt.
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Section 15.1 Forming Solutions A. Solubility Solubility of Polar Substances Ethanol is soluble in water because of the polar OH bond.
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Section 15.1 Forming Solutions A. Solubility Solubility of Polar Substances Why is solid sugar soluble in water?
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Section 15.1 Forming Solutions A. Solubility Substances Insoluble in Water Nonpolar oil does not interact with polar water. Water-water hydrogen bonds keep the water from mixing with the nonpolar molecules.
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Section 15.1 Forming Solutions A. Solubility How Substances Dissolve A “hole” must be made in the water structure for each solute particle. The lost water-water interactions must be replaced by water-solute interactions. “like dissolves like”
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Section 15.1 Forming Solutions B. Solution Composition: An Introduction The solubility of a solute is limited. –Saturated solution – contains as much solute as will dissolve at that temperature –Unsaturated solution – has not reached the limit of solute that will dissolve
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Section 15.1 Forming Solutions B. Solution Composition: An Introduction –Supersaturated solution – occurs when a solution is saturated at an elevated temperature and then allowed to cool but all of the solid remains dissolved Contains more dissolved solid than a saturated solution at that temperature Unstable – adding a crystal causes precipitation
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Section 15.1 Forming Solutions 1. Why do the temps. go from 0 to 100 o C? The normal liquid range for water is from 0 to 100 o C.
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Section 15.1 Forming Solutions 2. Which is the most soluble at 60 o C? Potassium iodide.
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Section 15.1 Forming Solutions 3. Which have the same solubility at 80 o C? Sodium chloride and potassium chlorate
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Section 15.1 Forming Solutions 4. Which changes the most from 0 to 100 o C? Potassium nitrate
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Section 15.1 Forming Solutions 5. Which changes the least from 0 to 100 o C? Sodium chloride
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Section 15.1 Forming Solutions 6. What is the solubility of potassium nitrate at 90 o C? 205 g / 100 cm 3 water
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Section 15.1 Forming Solutions 7. At what temp. does KI have a solubility of 150 g / 100 cm 3 ? about 12 -13 o C
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Section 15.1 Forming Solutions 8. Is a solution of 140 g NaNO 3 in 100 cm 3 water at 65 o C saturated, unsaturated, or supersaturated? supersaturated
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Section 15.1 Forming Solutions 9. You have a solution of KClO 4 containing 4 g at 65 o C. How many more grams to make it saturated? About 26 g more (from 4 g up to the line at 30 g)
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Section 15.1 Forming Solutions 10. A solution at 70 o C contains 200 g of KI. If cooled, when would crystals start forming? At about 42 o C.
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Section 15.1 Forming Solutions B. Solution Composition: An Introduction Solutions are mixtures. Amounts of substances can vary in different solutions. –Specify the amounts of solvent and solutes –Qualitative measures of concentration concentrated – relatively large amount of solute dilute – relatively small amount of solute
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Section 15.1 Forming Solutions B. Solution Composition: An Introduction Which solution is more concentrated? 3 / 1= 3 5 /1 = 5
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Section 15.1 Forming Solutions B. Solution Composition: An Introduction Which solution is more concentrated? 2 / 1 = 2 4 / 2 = 2 EQUAL
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Section 15.1 Forming Solutions C. Factors Affecting the Rate of Dissolving Surface area – by crushing a solid it creates more surface area Stirring – prevents particles in solution from reattaching to the crystal Temperature – more kinetic energy makes it easier for the particles to break away from the crystal
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