1 Announcements & Agenda (02/16/07) Please pick up exams if you haven’t. Mon: Movie in VDW 102– You must attend & complete a worksheet! Today Solution Concentrations (7.4, 7.5) Solution Concentrations (7.4, 7.5) Solution Properties & Some Other Mixtures (7.7) Solution Properties & Some Other Mixtures (7.7) Osmosis (7.7) Osmosis (7.7)

2 30 Good Practice Problems (Ch 7) 7.01, 7.03, 7.11, 7.13, 7.15, 7.17, 7.25, 7.27, 7.29, 7.31, 7.35, 7.37, 7.41, 7.45, 7.49, 7.53, 7.55, 7.61, 7.63, 7.65, 7.69, 7.71, 7.75, 7.77, 7.83, 7.87, 7.89, 7.93, 7.97, 7.99

3 Last Time: Nature of Solutions Solution – homogeneous mixture of two or more substances Solvent – the main medium, present in the largest quantity Solvent – the main medium, present in the largest quantity Solute – material dissolved in the solvent Solute – material dissolved in the solvent They don’t just have to be liquids:

4 Last Time: “Like Dissolves Like” What does this mean? Answer: compatibility of intermolecular forces (last week) Typically, compounds with similar polarity will be soluble in each other. Predicting trends based on properties…

5 Which of the following vitamins are fat-soluble and which are water soluble? Vitamins: organic molecules required for proper function but not made by the body. (Obtain by eating!) 2 categories: 2 categories: fat-soluble (dissolve in fatty hydrocarbon-like tissues) water-soluble Why we need at least some oil & fat in our diet!

6 In water, strong electrolytes produce ions and conduct an electric current.strong electrolytes produce ions and conduct an electric current. weak electrolytes produce a few ions.weak electrolytes produce a few ions. nonelectrolytes do not produce ions.nonelectrolytes do not produce ions. Last Time: Solutes & Ionic Charge

7 the maximum amount of solute that dissolves in a specific amount of solvent.the maximum amount of solute that dissolves in a specific amount of solvent. expressed as grams of solute in 100 grams of solvent water.expressed as grams of solute in 100 grams of solvent water. g of solute g of solute 100 g water Solubility & Concentration ( ) Unsaturated vs. Saturated Solutions

8 At 40  C, the solubility of KBr is 80 g/100 g H 2 O. Identify the following solutions as either 1) saturated or 2) unsaturated. Explain. A. 60 g KBr added to 100 g of water at 40  C. B. 200 g KBr added to 200 g of water at 40  C. C. 25 g KBr added to 50 g of water at 40  C. Learning Check What happens to the “leftover” solute???

9 Effect of Temperature on Solubility Depends on Temp!Depends on Temp! Solids: usually increases as temperature inc.Solids: usually increases as temperature inc. Gases: usually decreases as temperature inc.Gases: usually decreases as temperature inc.

10 Solubility and Pressure Henry’s Law: Gas solubility is directly related to gas pressure above the liquidGas solubility is directly related to gas pressure above the liquid at higher pressures, more gas molecules dissolve in the liquid.at higher pressures, more gas molecules dissolve in the liquid. Real life examples… soda, the bends, etc.

11 The amount of solute dissolved in a specific amount of solution. amount of solute amount of solution Comes in all sorts of fantastic flavors! Mass Percent Mass Percent Volume Percent Volume Percent Mass/Volume Percent Mass/Volume Percent Molarity Molarity Percent Concentration (7.4)

12 concentration is the percent by mass of solute in a solution.concentration is the percent by mass of solute in a solution. mass percent = g of solute x 100 g of solute + g of solvent g of solute + g of solvent amount in g of solute in 100 g of solution.amount in g of solute in 100 g of solution. mass percent = g of solute x 100 mass percent = g of solute x g of solution 100 g of solution Mass Percent (% m/m)

13 Mass of Solution 8.00 g KCl g KCl solution Add water to give g solution

14 Calculation of mass percent (% m/m) requires the grams of solute (g KCl) andgrams of solute (g KCl) and grams of solution (g KCl solution).grams of solution (g KCl solution). g of KCl = 8.00 g g of solvent (water) = g g of KCl solution = g 8.00 g KCl (solute) x 100 = 16.0% (m/m) 8.00 g KCl (solute) x 100 = 16.0% (m/m) g KCl solution g KCl solution Calculating Mass Percent

15 percent volume (mL) of solute (liquid) to volume (mL) of solution.percent volume (mL) of solute (liquid) to volume (mL) of solution. volume % (v/v) = mL of solute x 100 mL of solution solute (mL) in 100 mL of solution.solute (mL) in 100 mL of solution. volume % (v/v) = mL of solute 100 mL of solution Volume Percent (% v/v)

16 percent mass (g) of solute to volume (mL) of solution.percent mass (g) of solute to volume (mL) of solution. mass/volume % (m/v) = g of solute x 100 mL of solution solute (g) in 100 mL of solution.solute (g) in 100 mL of solution. mass/volume % (m/v) = g of solute x mL of solution Mass/Volume Percent (% m/v)

17 Percent Conversion Factors Two conversion factors can be written for each type of % value. TABLE 7.7 5% (m/v) glucose There are 5 g of glucose 5 g glucose and 100 mL solution in 100 mL of solution. 100 mL solution 5 g glucose

18 How many grams of NaOH are needed to prepare 75.0 g of 14.0% (m/m) NaOH solution? 1) 10.5 g NaOH 2) 75.0 g NaOH 3) 536 g NaOH 12345

19 1)10.5 g NaOH 75.0 g solution x 14.0 g NaOH = 10.5 g NaOH 100 g solution 100 g solution 14.0% (m/m) factor 14.0% (m/m) factor Solution

20 How many milliliters of a 5.75% (v/v) ethanol solution can be prepared from 2.25 mL ethanol? ) 2.56 mL 2) 12.9 mL 3) 39.1 mL

21 3) 39.1 mL 2.25 mL ethanol x 100 mL solution 5.75 mL ethanol 5.75% (v/v) inverted 5.75% (v/v) inverted = 39.1 mL solution Solution

22 Molarity and Dilution (7.5) Molarity (M) is a chemist’s concentration term for solutions.a chemist’s concentration term for solutions. gives the moles of solute in 1 L solution.gives the moles of solute in 1 L solution. moles of solutemoles of solute liter of solution

23 Preparing a 1.0 Molar Solution A 1.00 M NaCl solution is prepared by weighing out 58.5 g NaCl (1.00 mole) andby weighing out 58.5 g NaCl (1.00 mole) and adding water to make 1.00 liter of solution.adding water to make 1.00 liter of solution.

24 D ilution In a dilution water is added.water is added. volume increases.volume increases. concentration decreases.concentration decreases.

25 Comparing Initial & Diluted Solutions In the initial and diluted solution, the amount of solute is the same.the amount of solute is the same. the concentrations and volumes are related by the following equations:the concentrations and volumes are related by the following equations: For percent concentration: C 1 V 1 = C 2 V 2 initial diluted initial diluted For molarity: M 1 V 1 = M 2 V 2 initial diluted initial diluted

26 Summary: Properties of Solutions contain small particles (ions or molecules).contain small particles (ions or molecules). are transparent.are transparent. do not separate*.do not separate*. cannot be filtered.cannot be filtered. do not scatter light.do not scatter light.

27 Colloids have medium size particles.have medium size particles. cannot be filtered.cannot be filtered. can be separated by semipermeable membranes.can be separated by semipermeable membranes. scatter light (Tyndall effect).scatter light (Tyndall effect).

28 Examples of Colloids FogFog Whipped creamWhipped cream MilkMilk CheeseCheese Blood plasmaBlood plasma PearlsPearls

29 Suspensions have very large particles.have very large particles. settle out.settle out. can be filtered.can be filtered. must be stirred to stay suspended.must be stirred to stay suspended. Examples include blood platelets, muddy water, and lotions.

30 Osmosis water (solvent) flows from the lower solute concentration into the higher solute concentration.water (solvent) flows from the lower solute concentration into the higher solute concentration. the level of the solution with the higher concentration rises.the level of the solution with the higher concentration rises. the concentrations of the two solutions become equal with time.the concentrations of the two solutions become equal with time.

31 Suppose a semipermeable membrane separates a 4% starch solution from a 10% starch solution. Starch is a colloid and cannot pass through the membrane, but water can. What happens? semi-permeable membrane 4% starch Osmosis 10% starch H2OH2O

32 7% starch Water Flow Equalizes The 10% starch solution is diluted by the flow of water out of the 4% and its volume increases.The 10% starch solution is diluted by the flow of water out of the 4% and its volume increases. The 4% solution loses water and its volume decreases.The 4% solution loses water and its volume decreases. Eventually, the water flow between the two becomes equal.Eventually, the water flow between the two becomes equal. 7% starch H2OH2O

33 Osmotic Pressure produced by the solute particles dissolved in a solution.produced by the solute particles dissolved in a solution. equal to the pressure that would prevent the flow of additional water into the more concentrated solution.equal to the pressure that would prevent the flow of additional water into the more concentrated solution. greater as the number of dissolved particles in the solution increases.greater as the number of dissolved particles in the solution increases.

34 Osmotic Pressure of the Blood Red blood cells have cell walls that are semipermeable membranes.have cell walls that are semipermeable membranes. maintain an osmotic pressure that cannot change or damage occurs.maintain an osmotic pressure that cannot change or damage occurs. must maintain an equal flow of water between the red blood cell and its surrounding environment.must maintain an equal flow of water between the red blood cell and its surrounding environment.

35 Isotonic Solutions exerts the same osmotic pressure as red blood cells.exerts the same osmotic pressure as red blood cells. is known as a “physiological solution”.is known as a “physiological solution”. of 5.0% glucose or 0.90% NaCl is used medically because each has a solute concentration equal to the osmotic pressure equal to red blood cells.of 5.0% glucose or 0.90% NaCl is used medically because each has a solute concentration equal to the osmotic pressure equal to red blood cells. H2O H2O

36 Hypotonic Solutions has a lower osmotic pressure than red blood cells.has a lower osmotic pressure than red blood cells. has a lower concentration than physiological solutions.has a lower concentration than physiological solutions. causes water to flow into red blood cells.causes water to flow into red blood cells. causes hemolysis: RBCs swell and may burst.causes hemolysis: RBCs swell and may burst. H2OH2O

37 Hypertonic Solutions has a higher osmotic pressure than RBCs.has a higher osmotic pressure than RBCs. has a higher concentration than physiological solutions.has a higher concentration than physiological solutions. causes water to flow out of RBCs.causes water to flow out of RBCs. cause crenation: RBCs shrinks in size.cause crenation: RBCs shrinks in size. H2OH2O

38 Dialysis In dialysis, solvent and small solute particles pass through an artificial membrane.solvent and small solute particles pass through an artificial membrane. large particles are retained inside.large particles are retained inside. waste particles such as urea from blood are removed using hemodialysis (artificial kidney).waste particles such as urea from blood are removed using hemodialysis (artificial kidney).