Warm Up. 1. What causes the high surface tension of water? 2. In the formation of a solution, how does the solvent differ from the solute?

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1 Warm Up 1. What causes the high surface tension of water? 2. In the formation of a solution, how does the solvent differ from the solute? 3. Why are all ionic compounds electrolytes? 4. How do you write the formula for a hydrate? 5. What distinguishes a colloid from a suspension and a solution? 6. Could you separate a colloid by filtering? Explain. 7. What is the percent by mass of water in CuSO 4 *5H 2 O 1

2 16.1 PROPERTIES OF SOLUTIONS Factors that increase the rate of solution formation 1.) stirring 2.) temperature 3.) surface area To maximize the surface area of a substance, crush into fine powder Solubility maximum amount of solute that can be dissolved in a given amount of solvent at a constant temperature 1.) Saturated Solution contains exactly as much solute as the solvent can hold at a given temp. 2.) Unsaturated Solution solution has less than the maximum amount of solute that can be dissolved 3.) Supersaturated Solution contains more solute than can normally hold at a given temp. if even one more crystal of solute added to supersaturated solution, precipitate will form 2

3 Miscible two solutions that dissolve in each other (look like a single material) Immiscible liquids that will not dissolve in each other 3

4 Factors Affecting Solubility 1.) Polar & Nonpolar Solvents "like dissolves like" solution is most likely to form when solute & solvent are either both polar or both nonpolar ***Polar means that there is an unequal sharing of electrons in the bond between species 2.) Temperature solubility of solids increases as temperature of solvent increases Ex. making hot chocolate vs. pouring that packet into cold water 3.) Pressure increasing pressure on a gas increases its solubility in liquid Ex. carbonated soft drinks ***Refer to Solubility Chart on p. 474 Henry s Law at a given temp., solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid Directly proportional means that if one variable increases, then so does the other variable if one variable decreases, then so does the other variable Equation for Henry's Law S 1 = S 2 P 1 P 2 4

5 16.2 CONCENTRATIONS OF SOLUTIONS Concentration amount of solute dissolved in a certain amount of solvent Dilute Solutions contains a little solute Concentrated Solutions contain a lot of solute Molarity M number of moles of solute per liter of solution (aka molar concentration) Molarity (M) = moles of solute liters of solution 5

6 Sample Problem Intravenous (IV) saline solutions are often administered to patients in the hospital. One saline solution contains 0.90 g NaCl in exactly 100 ml of solution. What is the molarity of the solution? Dilutions process of reducing the concentration of a solute in solution, usually simply by mixing with more solvent (total moles of solute is not changed) M 1 V 1 = M 2 V 2 6

7 Sample Problem How many milliliters of aqueous 2.00 M MgSO 4 solution must be diluted with water to prepare ml of aqueous M MgSO 4? Percent Solutions Volume Volume Percent by volume (% v/v) = (volume of solute / volume of solution) X 100 Mass Mass Percent by mass (% m/m) = (mass of solute / mass of solution) X 100 7

8 Sample Problem What is the percent by volume of ethanol (C 2 H 6 O, or ethyl alcohol) in the final solution when 85 ml of ethanol is diluted to a volume of 250 ml with water CALCULATIONS INVOLVING COLLIGATIVE PROPERTIES Molality m number of moles of solute dissolved in 1 kilogram of solvent (aka molal concentration) Molality = moles of solute kilogram of solvent 8

9 Sample Problem How many grams of potassium iodide must be dissolved in g of water to produce a 0.06 molal KI solution? Mole Fractions ratio of moles of that solute to the total number of moles of solvent & solute X A = (n A / n A + n B ) X B = (n B / n A + n B ) 9

10 Practice Problem Ethylene glycol is added to automobile cooling systems to protect against cold weather. What is the mole fraction of each component in a solution containing 1.25 mol of ethylene glycol (EG) and 4.00 mol water? 10