Edward Wen Solutions

2 Learning Outcomes Solutions (applying solubility rules, calculations with concentrations and dilutions) Definition and description of the properties of Colloids Definition and description of the properties of Suspensions Osmotic pressure effects on cells – defining isotonic, hypotonic, hypertonic

3 Solution Homogeneous mixtures composition may vary from one sample to another appears to be one substance, though contains multiple materials most Homogeneous materials are actually Solutions Gas state: common air Liquid: Gasoline (dozens of compounds), Soda water (sugar or asparatame, CO2, citric acid, fructose) Solid: Alloy such as brass

4 SolutionsSolutions: Solute + Solvent Solute: the dissolved substance. Sugar in Soda seems to “disappear” “takes on the state” of the solvent Solvent: the substance solute dissolves in. Water in Soda does not appear to change state Aqueous solutions: solutions in which the solvent is water.

5 Common Types of Solution Solution Phase Solute Phase Solvent PhaseExample Gaseous solutionsgas air (mostly N 2 & O 2 ) Liquid solutions gas liquid solid liquid soda (CO 2 in H 2 O) vodka (C 2 H 5 OH in H 2 O) seawater (NaCl in H 2 O) Solid solutionssolid brass (Zn in Cu) Alloys: solutions that contain Metal solutes and a Metal solvent, such as Nickel (5 cents of 1$), Brass, Stainless steel

6 How Soluble? Solubility Soluble: when one substance (solute) dissolves in another (solvent)  Homogeneous Salt and Sugar are soluble in water: Saline and Soda Acetic acid (HC 2 H 3 O 2 ) in water: Vinegar Oxygen gas in Nitrogen gas: Air Insoluble: when one substance does not dissolve in another  Heterogeneous Oil is insoluble in water: Italian salad dressing

7 Will It Dissolve? Chemist’s Rule of Thumb – Like Dissolves Like a chemical will dissolve in a solvent if it has a similar structure to the solvent when the solvent and solute structures are similar, the solvent molecules will attract the solute particles at least as well as the solute particles to each other

8 Classifying Solvents SolventClass Structural Feature Water, H 2 OpolarO-H Ethyl Alcohol, C 2 H 5 OHpolarO-H Acetone, C 3 H 6 OpolarC=O Toluene, C 7 H 8 nonpolarC-C & C-H Hexane, C 6 H 14 nonpolarC-C & C-H

9 Solubility in Water, A Polar Solvent? Ionic compound (Yes): Ions are attracted to polar Water. Salt NaCl dissolve in water Polar molecules (Yes): attracted to polar solvents table Sugar, Alcohol, glucose Nonpolar molecules are NOT attracted to Water  -carotene, (C 40 H 56 ), is not water soluble; it dissolves in fatty (nonpolar) tissues Those molecules with both polar and nonpolar structures: depends on structural features in the molecule

10 Salt Dissolved in Water

11 Solubility Definition: the maximum amount of solute that can be dissolved in a given amount of solvent Usually a limit to the solubility of one substance in another Exceptions: gases are always soluble in each other two liquids that are mutually soluble are said to be miscible  alcohol and water are miscible  oil and water are immiscible

12 Descriptions of Solubility Saturated solutions have the maximum amount of solute that will dissolve in that solvent at that temperature Unsaturated solutions can dissolve more solute Supersaturated solutions are holding more solute than they should be able to at that temperature unstable

13 Solubility of Solid Depends on Temperature Higher temp  higher solubility of solid in liquid Lower temp  higher solubility of gas in liquid

14 Solubility of Gases Decreases at higher Temperature Observation 1: Warm soda pop fizzes more than cold soda pop Cause: Solubility of CO 2 in water decreases as temperature increases. Observation 2: When water is heated up, gas bubbles appear even before boiling occurs. Cause: Solubility of air in water decreases as temperature increases.

15 Solubility of Gas depends on Pressure Henry’s Law: higher pressure = higher solubility CO 2 is dissolved under Pressure into bottled/canned soda

Under which conditions does sugar have the best solubility? A.high temperature and high pressure B.high temperature and low pressure C.low temperature and low pressure D.low temperature and high pressure

Under which conditions does oxygen gas have the best solubility? A.high temperature and high partial pressure (P O 2 ) B.high temperature and low partial pressure C.low temperature and low partial pressure D.low temperature and high partial pressure

18 Solution Concentration Descriptions Concentrated solutions have high solute concentrations. Example: Soda syrup before mixed with carbonated water. Diluted solutions have low solute concentrations. Example: Soda drink from adding carbonated water to syrup

19 Concentrations – Quantitative Descriptions of Solutions Solutions have variable composition. Salt vs. Water in Seawater To describe a solution accurately, you need to describe the components and their relative amounts Concentration = amount of solute in a given amount of solution Seawater: Salt concentration 3.4% Dead Sea: Salt concentration 30% Vinegar: Acetic acid concentration 5%

20 Weight/Volume Percent (w/v)% mass of solute (gram) in every 100 mL of solution Vinegar is 5% (w/v) solution of acetic acid by mass, then there are 5 grams of acetic acid in every 100 mL of vinegar

21 Information Given:0.35 g phenol. 25 mL solution Find:(w/v)% Example: Chloraseptic sore throat spray contains 0.35 g of phenol in 25 mL of solution. Find the weight/volume percent concentration of phenol.

22 Volume/Volume Percent (v/v)% Volume of solute (mL) in every 100 mL of solution Common rubbing alcohol is 50~91% (v/v) solution of isopropanol (or 2- propanol) in every 100 mL of solution.

23 Information Given:101 mL ethanol, 750 mL solution (wine) Find:(v/v)% Example: A 750-mL bottle of wine contains 101 mL of ethanol. Find the volume/volume percent concentration of ethanol.

24 Mass Percent (%) mass of solute (gram) in every 100 gram of solution if a solution is 0.9% by mass, then there are 0.9 grams of solute in every 100 grams of solution Mass of solution = Mass of solute + Mass of solvent

25 = % Information Given:27.5 g C 2 H 6 O; 175 g H 2 O Find:% by mass Eq’n: Example: Calculate the mass percent of a solution containing 27.5 g of ethanol (C 2 H 6 O) and 175 g of H 2 O = 13.6%

26 Parts per million (ppm) concentration mass of solute (gram) in every 1,000,000 gram of solution Or volume of solute (mL) in every 1,000,000 milliliter of solution

27 Using Concentrations as Conversion Factors concentrations show the relationship between the amount of solute and the amount of solvent 12% by mass sugar(aq) means 12 g sugar  100 g solution The concentration can then be used to convert the amount of solute into the amount of solution, or visa versa

28 Information Given:85.2 g C 12 H 22 O 11 Find:mL sol’n CF:11.5 g C 12 H 22 O 11  100 mL sol’n SM: g sucrose → g sol’n → mL sol’n Example: A soft drink contains 11.5% (w/v) sucrose (C 12 H 22 O 11 ). What volume of soft drink in milliliters contains 85.2 g of sucrose? 741 mL

29 Information Given:500. mL rubbing alcohol Find:mL sol’n CF:85 g isopropanol  100 mL rubbing alcohol Example: Rubbing alcohol contains 85% (v/v) isopropanol. What volume of isopropanol is contained in 500. mL rubbing alcohol? 4.3 x 10 2 mL

30 Molarity Concentration READ the label in the reagent bottle READ the label in the reagent bottle! “What does ‘6 M HCl’ mean?” Definition: Moles of solute per 1 liter of solution Purpose: describing how many molecules of solute in each liter of solution Unit: mole/L, abbreviated as “M”. If a sugar solution concentration is 2.0 M, 1 liter of solution contains 2.0 moles of sugar, 2 liters = 4.0 moles sugar, 0.5 liters = 1.0 mole sugar molarity = moles of solute liters of solution

31 Why Molarity? Many reagents used in chemistry, even many biology labs, are in the form of solution. Molarity concentration of solution is particularly important and useful because Easy to prepare a solution to a given molarity Easy to use: To obtain given amount (mole) of reagent, just calculate the volume of solution to be used: Volume (L) = mole  molarity

Example: Calculating Molarity

33 Information Given:250 mL solution; 15.5 g NaCl NaCl; Example: Calculate the molarity of a solution made from 15.5 g of NaCl in 250 mL solution M NaCl

34 Calculations involving Molarity Molarity = mole  Volume (L) Solve for mole: Mole = Molarity  Volume (L) Solve for volume of solution in liters: Volume (L) = mole  molarity

35 Information Given:1.24 mol NaOH Find: L solution CF:0.114 mol = 1 L SM: mol → L Example: How many liters of a M NaOH solution contains 1.24 mol of NaOH?

36 Information Given: M (NH 4 ) 2 S solution V = mL Find: mol (NH 4 ) 2 S CF: mol = 1 L Example: How many moles of (NH 4 ) 2 S are in 11.25mL M (NH 4 ) 2 S solution? mol

37 Information Given: M NaCl solution V = mL Find: gram NaCl CF:1 L = mol 1 mol NaCl = g NaCl Example: How many grams of NaCl are in mL M NaCl solution? g

When mixing more solvent into a solution, the volume of final solution is greater than the original solution The mole of solute remains the same before and after mixing more solvent The final concentration of solution is lower than in the beginning (diluted) DilutionDilution: More Solvent Added

Making a Solution by Dilution M 1 x V 1 = M 2 x V 2 Dilution: mole solute is the same = M 1 x V 1 = M 2 x V 2 Example: A student added 1.00 L water to 2.00 L 1.00 M HCl. The final volume became 3.00 L. What is the final concentration? M.

40 Example: Making solution from concentrate: What Volume of 12.0 M KCl Is Needed to Make 5.00 L of 1.50 M KCl Solution? Given: Initial solutionFinal solution Concentration12.0 M1.50 M Volume? L5.00 L

41 Example—Determine the Concentration of the Solution after dilution A solution made by diluting 125 mL of 0.80 M HCl to 500 mL. M 2 = 0.20 M

Physical Properties Affected by Concentration Change in Concentration affects the physical properties of solution. Vapor pressure of solvent Freezing point of solution Osmotic pressure

Boiling Point Elevation: Reduced evaporation in solution A liquid solution containing a nonvolatile solute has higher boiling point than the pure solvent

Freezing point Depression A water-antifreeze mixture has a higher boiling point and lower freezing point than pure water. This will reduce the chance of engine coolant being frozen or being evaporated too quickly. Spray salt on icy road help preventing ice on the road. A liquid solution containing a nonvolatile solute has lower freezing point than the pure solvent.

Osmosis Higher concentration of solution has stronger tendency to uptake solvent The liquid level in the tube rises until equilibrium is reached.

Osmosis Semi-permeable membrane separating (a) pure water and a salt-water solution, and (b) a dilute salt-water solution. Worm cruelty: salt on earthworm or snail too.salt on earthworm

Osmotic Pressure and Reverse Osmosis (RO) Osmotic pressure is the amount of pressure needed to prevent the solution in the tube from rising as a result of the process of osmosis. RO: When the added pressure exceeds the osmotic pressure, pure water leaves the concentrated solution.

8 | 48 Red blood cell in NaCl solutions (a) Hyptonic solution. In pure water, cell absorbs water and swells. (b) Crenation in concentrated sodium chloride solution. Cell loses water and collapses. (c) Cells neither swell nor shrink in physiological saline solution. Copyright David M. Phillips/Visuals Unlimited

Dialysis Through the semipermeable membrane, there is a net movement of ions and small molecules from a region of higher concentration to a region of lower concentration. Larger molecules such as protein remains inside the membrane.

8 | 50 Dialysis in Real World