1. Solutions
Edward Wen

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. Solutions: 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 Phase
Example
Gaseous solutions
gas
air (mostly N2 & O2)
Liquid solutions
liquid
solid
soda (CO2 in H2O)
vodka (C2H5OH in H2O)
seawater (NaCl in H2O)
Solid solutions
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 (HC2H3O2) 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? Like Dissolves Like Chemist’s Rule of Thumb –
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 Solvent Class Structural Feature Water, H2O polar
O-H
Ethyl Alcohol, C2H5OH
Acetone, C3H6O
C=O
Toluene, C7H8
nonpolar
C-C & C-H
Hexane, C6H14

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
b-carotene, (C40H56), 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 CO2 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
CO2 is dissolved under Pressure into bottled/canned soda

16. Under which conditions does sugar have the best solubility?
high temperature and high pressure
high temperature and low pressure
low temperature and low pressure
low temperature and high pressure

17. Under which conditions does oxygen gas have the best solubility?
high temperature and high partial pressure (PO2)
high temperature and low partial pressure
low temperature and low partial pressure
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. Given: 0.35 g phenol. 25 mL solution Find: (w/v)%
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. Given: 101 mL ethanol, 750 mL solution (wine) Find: (v/v)%
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. Example: Calculate the mass percent of a solution containing 27
Example: Calculate the mass percent of a solution containing 27.5 g of ethanol (C2H6O) and 175 g of H2O
Information
Given: 27.5 g C2H6O; 175 g H2O
Find: % by mass
Eq’n:
= %
= 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. Example: A soft drink contains 11. 5% (w/v) sucrose (C12H22O11)
Example: A soft drink contains 11.5% (w/v) sucrose (C12H22O11). What volume of soft drink in milliliters contains 85.2 g of sucrose?
Information
Given: 85.2 g C12H22O11
Find: mL sol’n
CF: 11.5 g C12H22O11  100 mL sol’n
SM: g sucrose → g sol’n → mL sol’n
741 mL

29. Example: Rubbing alcohol contains 85% (v/v) isopropanol
Example: Rubbing alcohol contains 85% (v/v) isopropanol. What volume of isopropanol is contained in 500. mL rubbing alcohol?
Information
Given: 500. mL rubbing alcohol
Find: mL sol’n
CF: 85 g isopropanol  100 mL rubbing alcohol
4.3 x 102 mL

30. Molarity Concentration
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 31

32. Example: Calculate the molarity of a solution made from 15
Example: Calculate the molarity of a solution made from 15.5 g of NaCl in 250 mL solution.
Information
Given: 250 mL solution; 15.5 g NaCl NaCl;
1.06 M NaCl

33. 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 33

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

35. Example: How many moles of (NH4)2S are in 11. 25mL 0
Example: How many moles of (NH4)2S are in 11.25mL M (NH4)2S solution?
Information
Given: M (NH4)2S solution
V = mL
Find: mol (NH4)2S
CF: mol = 1 L
mol

36. Example: How many grams of NaCl are in 10. 00 mL 0
Example: How many grams of NaCl are in mL M NaCl solution?
Information
Given: M NaCl solution
V = mL
Find: gram NaCl
CF: 1 L = mol
1 mol NaCl = g NaCl g

37. Dilution: More Solvent Added
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)

38. Making a Solution by Dilution
Dilution: mole solute is the same = M1 x V1 = M2 x V2
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?
0.667 M.

39. Example: Making solution from concentrate: What Volume of 12
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 solution Final solution
Concentration M M
Volume ? L L

40. Example—Determine the Concentration of the Solution after dilution
A solution made by diluting 125 mL of 0.80 M HCl to 500 mL.
M2 = 0.20 M

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

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

43. Freezing point Depression
A liquid solution containing a nonvolatile solute has lower
freezing point than the pure solvent.
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.

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

45. 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.

46. 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.

47. Red blood cell in NaCl solutions
Copyright David M. Phillips/Visuals Unlimited
(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.

48. 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.

49. Dialysis in Real World

50. Colloid and Suspension
Tyndall effect:
Examples of colloid: Smoke, cloud, fog,