1. Solutions (Chapter 16)
Dr. Walker

2. What will you learn? New terminology for mixtures
How to separate mixtures
How to determine solution concentrations

3. A Review…. What is a mixture? What are two kinds of mixtures?
A combination of two or more compounds
What are two kinds of mixtures?
Homogeneous: evenly distributed
Heterogeneous: not evenly distributed

4. New Terminology Solution Another term for a homogeneous mixture
Associated with liquids, but can have a gaseous solution (i. e., air)
Can have a solid-solid solution
Alloy: mixture of metals
Steel = Iron + Carbon
Brass = Copper + Zinc
Bronze = Tin + Aluminum

5. Solution Examples States of matter in solution Example gas in gas
air ( N2, O2 , Ar, CO2 , other gases)
gas in liquid
soda (CO2 in water)
liquid in liquid
gasoline (a mixture of hydrocarbon compounds)
solid in liquid
sea water ( NaCl and other salts in water)
gas in solid
H2 in platinum or palladium
liquid in solid
dental amalgams ( mercury in silver)
solid in solid
alloys ( brass, (Cu/Zn), solder (Sn/Pb)

6. New Terminology Miscible
Liquids that are soluble in any proportion and form a solution
Example: Water and alcohol – you can have 90% water or 90% alcohol and it will dissolve either way. Solids have a limit to how much can dissolve. Miscible liquids do not!

7. Parts of a Solution The chemical that is dissolved is the solute
The chemical that does the dissolving is the solvent (majority component)

8. Solution Examples Soda What is the solvent?
Water
What is (are) the solute(s)?
Carbon dioxide
Sugar
Flavorings
Preservatives

9. Colloids Homogeneous mixture with large particles
They look murky (you can’t see through them) and scatter light (fog vs. headlights)
Solutions are clear (if liquid or gas)
Examples:
Fog
Milk
Soap

10. Separating Mixtures Decanting
Pour off the solvent, leave the solute. Used in suspensions. An example of this is dirt in water. Once the dirt settles, the water can be carefully poured off, leaving the dirt.
Suspension = heterogeneous mixture

11. Separating Mixtures Filtration:
Mixture of
solid and
liquid
Stirring
rod
Filtrate (liquid
component
of the mixture)
Filter paper
traps solid
Funnel
Filtration:
A piece of paper is placed in a funnel. The suspension is poured in. The solvent passes through, the solid solute gets caught in the funnel. Separates by particle size using paper.
The most common example of this is making coffee. The water passes through the filter and picks up soluble components in the coffee. The grounds are left in the coffee filter.
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 40

12. Separating Mixtures Centrifuge Evaporation
Separates components of a mixture with different densities by spinning at very high speed. These are used to separate components in blood (plasma, platelets, etc.).
Evaporation
If you have a salt water solution, if you evaporate the water, you’re left with the salt.

13. Biological Centrifuge Equipment

14. Separating Mixtures Chromatography
Separates mixtures based on adhesion of compounds to a solid (how well compounds stick to something). An example is separating dyes in inks. The different inks move at a different rate through special paper (the solid) based on their chemical structure.

15. Chromatography

16. Chromatography

18. Separating Mixtures Distillation
Separates solutions based on differences in boiling point.
Fermentation of sugar in water produces alcohol, which is found in beer, wine, etc. An alcohol/water mixture boils at a lower temperature than water, so it separates out.
Another example is separating different petroleum products from crude oil.

19. Distillation Apparatus

21. Solubility “Like Dissolves Like” Polar solvents dissolve polar solutes
Water and alcohol are both polar and they are miscible
Nonpolar solvents dissolve nonpolar solutes
Oil and gas are soluble, some small engines require premixing
Polar + Nonpolar = no mixing!
Think “oil and water” – they don’t mix!
Italian salad dressing = oil and vinegar = two layers!

22. Molecular Polarity

23. Polarity Review Polar molecules Nonpolar molecules
Difference in electronegativity
Three dimensional asymmetry
Covalent: Bent (H2O), Trigonal Pyramidal (NH3) shapes
Compounds with oxygen and nitrogen (electronegative elements)
Ionic compounds polar by default
Nonpolar molecules
Tetrahedral (CCl4) shape
Hydrocarbons (CH4, C3H8, C8H18)

25. Solubility Solubility
The maximum amount of a substance that will dissolve in a given amount of solvent at a specified temperature.
How much solute does it have?
Unsaturated: It could hold more solute than it has
Saturated: It has the maximum amount of solute
Supersaturated: It has “too much” solute
Supersaturated solutions crystallize when disturbed
More stable at high temperatures

26. Solubility Curves Different compounds have different solubilities
More of some things can dissolve than others

27. Solubility Curves Which has the highest solubility at 90 oC?
Which has the highest solubility at at 20 oC?
On which material does temperature have the lowest effect on solubility?

28. Solubility Curves Which has the highest solubility at 90 oC? KNO3
Which has the highest solubility at at 20 oC? NaClO3
On which material does temperature have the lowest effect on solubility? NaCl

29. Solubility Solubility in a solvent is usually dependent on:
Temperature
More solute can dissolve at a higher temperature (in most cases)
Example: more sugar can dissolve in boiling water than room temperature water
Surface area
Solute dissolves faster with more surface area
Crystalline sugar dissolves faster than sugar cubes – more interaction with the solvent

30. Colligative Properties
Colligative properties are properties of a solution that change with the addition of solute or when the solute concentration changes
Freezing Point Depression
Boiling Point Elevation
Vapor Pressure
The number of solute particles changes the freezing point and boiling point of a pure substance.

31. A Real World Example Antifreeze Ethylene Glycol
Increases boiling point (works as coolant)
Decreases freezing point (works as antifreeze)
Concentration dependent

32. A Real World Example Calcium Chloride (CaCl2)
Used to melt icy roads, mixed with sand
Works by decreasing the freezing point of water

33. A Real World Example Boiling Point Changes with Elevation
Higher altitude = lower pressure
Less atmosphere pushing down
Boiling point for water at sea level = 100 C
Boiling point for water in Denver (1 mile up) = 95 C
Boiling point for water on Mt. Everest (5 miles up) = 72 C

34. Concentration Amount of material dissolved in a solvent
Several potential units
Molarity (moles solute per liter solution)
Molality (liters solute per kg solvent)
Parts per million

35. Molarity
We will use molarity

36. Molarity
The equation includes moles and liters, so information MUST be in these units before plugging into the equation
If grams are given, divide by molar mass to get moles
If milliliters are given, divide by 1000 to get liters

37. Molarity Example #1
Give the molarity of a solution containing 0.25 moles NaCl with a total volume of 0.2 L.

38. Molarity Example #1
Give the molarity of a solution containing 0.25 moles NaCl with a total volume of 0.2 L.
M = = 1.25 M
0. 25 moles
___________
0.2 L

39. Molarity Example #2
Give the molarity of a solution containing 7.45 g KCl with a total volume of 400 mL

40. Molarity Example #2
Give the molarity of a solution containing 7.45 g KCl with a total volume of 400 mL
Convert units
(7.45 g / g/mole)
__________________
(400 mL / 1000 mL)
M =
= 0.25 M

41. Molarity Example #3
How many moles of CaO are contained in 0.8 L of a 0.25 M solution?

42. Molarity Example #3
How many moles of CaO are contained in 0.8 L of a 0.25 M solution?
moles
_________
0.8
0.25 M =
Moles = 0.2

43. Molarity Example #4
How many grams of glucose (C6H12O6) are required to make 500. mL of a 0.20 M solution?

44. Molarity Example #4
How many grams of glucose (C6H12O6) are required to make 500. mL of a 0.20 M solution?
Plug in and find moles first
Convert to grams with molar mass
moles
_________
(500 mL / 1000 )
Moles = 0.1
0.1 moles x g/mole = 18.0 g
0.2 M =

45. Dilutions
Sometimes you have to use a solution at one concentration to make a more dilute one
Or the some of the solution evaporates and the concentration changes
You have to figure out how much solvent to add

46. Dilutions Dilutions M1V1 = M2V2 The long way The short way
Find unknown from the molarity equation
Plug into second molarity equation
We won’t do this!
The short way
M = concentration (Molarity), V = volume
Dilutions M1V1 = M2V2

47. Dilution Example
What volume of a 3.0 M solution of HCl is required to make 500 mL of 0.5 M HCl?

48. Dilution Example
What volume of a 3.0 M solution of HCl is required to make 500 mL of 0.5 M HCl?
The numbers that go together and M1 and V1
M1V1 = M2V2
(0.5 M)(500 mL) = (3.0 M)V2
V2 = mL

49. Dilution Example
300 mL of a 1.5 M sucrose solution is allowed to sit on the countertop. After 24 h, 50 mL has evaporated. What is the new concentration of the solution?

50. Dilution Example
300 mL of a 1.5 M sucrose solution is allowed to sit on the countertop. After 24 h, 50 mL has evaporated. What is the new concentration of the solution?
M1V1 = M2V2
(1.5 M)(300 mL) = M2(300 – 50 mL)
1.8 M = M2

51. Dilution Example
A student has 50 mL of 2.0 M H2SO4. If the student adds 150 mL of water to this, what is the new concentration?

52. Dilution Example
A student has 50 mL of 2.0 M H2SO4. If the student adds 150 mL of water to this, what is the new concentration?
V1 = 50 mL
M1 = 2.0 M
V2 = = 200 mL
M2 = (50 mL)(2.0 M)/200 mL = 0.5 M

53. Terms To Know Solute Boiling Point Elevation Solvent Unsaturated
Solution Saturated
Suspension Supersaturated
Alloy
Decanting
Filtration
Centrifuge
Chromatography
Distillation
Solubility
Freezing Point Depression

54. Skills To Master Differentiating solutions and suspensions
Determining the solute and solvent in a solution
Determining the appropriate separation method for a given system
Determining solubility based on polarity
Calculating solution concentration, moles, or volume using the molarity equation
Calculating a new volume or concentration based on a given solution using the dilution equation