1. Solutions and Colloids
Homogeneous (or nearly homogeneous) Mixtures

2. Solutions Homogeneous mixtures Solvent = dissolving medium
often liquid; frequently water
gas in air and other gas solutions
rarely a solid
Solute(s) = dissolved material(s)
solids, liquids, and/or gases
often more than one solute

3. Water as Solvent Form aqueous solutions
Many biological fluids are solutions or have solution components
One of best solvents for dissolving ionic substances
Poor solvent for non-polar covalent substances.

4. Water O “H-bonding” binds water molecules tightly. H O H H O O H O H+ -
“H-bonding” binds water molecules tightly. H O - + O H + - O H + - O H -

5. Water Water is one of best solvents for ionic material (electrolytes)
Water’s polar molecular structure interacts strongly with charged ions
Water---Ion attractions replace ion---ion and water---water attractions with little net energy change

6. Water
Crystal’s +/- attractions cause lattice energy, which must be overcome to break up crystal.
Na+
Cl-

7. Water
Na+
Cl-

8. Water
“Void” weakens crystal and makes it more likely to break up in vicinity.
Several more H2O molecules may associate
Na+
Cl-

9. Water
Na+
Cl-

10. Water
Na+
Cl-

11. Water
Note: Positive ions associate with negative ends of waters, and negative ions associate with positive ends of waters.
+/- forces release energy
Na+
Cl-

12. Water In similar fashion, the entire crystal dissolves
positive ions link to oxygen of water
negative ions link to hydrogen of water
process call hydration
Hydration releases energy
Hydration energy compensates for lattice energy.

13. Water

14. Water An exothermic dissolving process.
Hydration energy is greater than lattice energy.

15. Water

16. Water An endothermic dissolving process.
Lattice energy is greater than hydration energy.

17. Water Exothermic processes release energy
Temperature of surroundings increase.
Hydration energy grater than lattice energy.
Endothermic processes absorb energy.
Temperature of surroundings decrease.
Lattice energy greater than hydration energy.

18. Solution Concentrations
Dilute
Small amount of solute for given solvent
Concentrated
Large amount of solute for given solvent
Saturated
Maximum amount of solute for given solvent
But these terms are qualitative, not quantitative, and are open to interpretation.

19. Solution Concentrations
20 gal. .

20. Solution Concentrations.
Dilute or Concentrated???

21. Solution Concentrations. .
Dilute or Concentrated???

22. Solution Concentrations
It depends, of course, on one’s point of view.
It’s only a teaspoon in 20 gallons.
Dilute??
But this concentration is far beyond the lethal dose for the fish.
Concentrated???

23. Solution Concentrations
Expressed as a ratio of the amount of solute to the total amount of solution:
grams
Amount of solute
Concentration =
Total amount of solution
(%, w/v) mL

24. Solution Concentrations
Expressed as a ratio of the amount of solute to the total amount of solution:
mass (grams)
Amount of solute
Concentration =
Total amount of solution
(%, w/w)
mass unit (grams)

25. Solution Concentrations
Expressed as a ratio of the amount of solute to the total amount of solution: mg
Amount of solute
Concentration =
Total amount of solution
( mg %) dL

26. Solution Concentrations
Expressed as a ratio of the amount of solute to the total amount of solution:
moles
Amount of solute
Concentration =
Total amount of solution
( molarity, M)
Liters

27. Solution Concentrations
% Concentration has multiplier of 100 to place ratio on “parts per 100” basis:
Grams of solute
mL of solution
%, w/v =
X 100

28. Solution Concentrations
‰ Concentration has multiplier of 1000 to place ratio on “parts per 1000 total” basis:
Grams of solute
mL of solution
‰ =
X 1000

29. Solution Concentrations
ppm concentration has multiplier of 106 to place ratio on “parts per million total” basis:
Grams of solute
mL of solution
ppm =
X 106

30. Solution Concentrations
Practice situation:
4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution.
What is the % (w/v) concentration of this solution?
Grams of solute
mL of solution
%, w/v =
X 100
4.75 g
% =
X 100
= %
750 mL
The g/mL units are understood but not included.

31. Solution Concentrations
4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution.
What is the % (w/v) concentration of this solution?
0.633%
NaCl
The concentration is % (w/v).
750 mL

32. Solution Concentrations
Another:
12.5 grams of H2SO4 is dissolved in sufficient water to make liters of solution.
What is the % (w/v) concentration of this solution?
Grams of solute
mL of solution
%, w/v =
X 100
Solution volume units must be converted from liters to mL before doing calculations: L = 500 mL.
12.5 g
% =
X 100
= 2.50 %
500 mL
The g/mL units are understood but not included.

33. Solution Concentrations
Once known, the solution concentration works as a conversion factor.
Establishes the “relationship” between amount of solute and volume of solution.
For % (w/v) concentrations, conversion factors derive from this relationship:
“%-Value” grams of solute = 100 mL solution

34. Solution Concentrations
Once known, the solution concentration work as a conversion factor.
Examples (all are wt/vol percents):
0.85 % NaCl
means…
0.85 g NaCl = 100 mL solution
and the conversion factors are…
0.85 g NaCl
100 mL solution
0.85 g NaCl
100 mL solution or

35. Solution Concentrations
Using the concentration as a conversion factor:
Examples (all are wt/vol percents):
What mass of NaCl is present in 2000 mL of 0.85% NaCl solution?
0.85%
NaCl
How much dissolved NaCl is in this 2000 mL of saline solution?

36. Solution Concentrations
Using the concentration as a conversion factor:
Examples (all are wt/vol percents):
What mass of NaCl is present in 2000 mL of 0.85% NaCl solution?
0.85 g NaCl
100 mL solution
2000 mL soln X =
17.0 g NaCl

37. Solution Concentrations
Using the concentration as a conversion factor:
Examples (all are wt/vol percents):
What mass of NaCl is present in 2000 mL of 0.85% NaCl solution?
0.85%
NaCl
17.0 grams of dissolved NaCl is present in 2000 mL of this solution

38. Solution Concentrations
Using the concentration as a conversion factor:
Examples (all are wt/vol percents):
What volume of 0.85% NaCl solution should contain 2.50 grams of dissolved NaCl?
0.85%
NaCl
What volume will contain 2.50 grams of dissolved NaCl?

39. Solution Concentrations
Using the concentration as a conversion factor:
Examples (all are wt/vol percents):
What volume of 0.85% NaCl solution should contain 2.50 grams of dissolved NaCl?
0.85 g NaCl
100 mL solution
2.50 g NaCl X =
294 mL soln

40. Solution Concentrations
Using the concentration as a conversion factor:
Examples (all are wt/vol percents):
What volume of 0.85% NaCl solution should contain 2.50 grams of dissolved NaCl?
0.85%
NaCl
294 mL of this solution contains 2.50 grams of dissolved NaCl.

41. Solution Concentrations
Three types of calculations dealing with concentrations:
Given the amount of solute and total solution, determine the concentration.
Given the concentration and amount of solution, find the amount of solute.
Given the concentration and the amount of solute, determine the amount of solution.

42. Solution Concentrations
Three types of calculations dealing with concentrations: 2
Concentration =
Amount of solute
Total amount of solution 3 1

43. Solution Concentrations
Given any two, be able to calculate the third: 2
Concentration =
Amount of solute
Total amount of solution 3 1

44. Solution Concentrations
Molarity
M =
Moles of solute
Liters of solution
4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution.
What is the molarity of NaCl in this solution?
We previously determined this solution to be 0.633%; what is its molarity?

45. Solution Concentrations
Molarity
M =
Moles of solute
Liters of solution
The 4.75 grams of NaCl will need to be converted to moles before the calulations are done.
Similarly, to make units match, the 750 mL will be converted to liters.

46. Solution Concentrations
Molarity
M =
Moles of solute
Liters of solution
4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution. M = ?
58.5 g NaCl
1 mole NaCl
4.75 g NaCl X =
mole NaCl
1000 mL
1 Liter
750 mL X =
0.750 L

47. Solution Concentrations
4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution. M = ?
M =
Moles of solute
Liters of solution
mole NaCl
0.750 L
M =
moles NaCl
0.750 Liters of solution
= M NaCl
= moles NaCl/L

48. Solution Concentrations
4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution.
What is the % (w/v) concentration of this solution and what is its molarity?
0.633%
0.108 M
NaCl
The concentration is % (w/v)
and…
is M
750 mL

49. Solution Concentrations
Given any two, be able to calculate the third: 2
Concentration =
Amount of solute
Total amount of solution 3 1

50. Solution Concentrations
Using the concentration as a conversion factor:
Examples (all are wt/vol percents):
How many moles of NaCl is present in 2000 mL of M NaCl solution?
0.225M
NaCl
How much dissolved NaCl is in this 2000 mL of saline solution?

51. Solution Concentrations
Using the concentration as a conversion factor:
How many moles of NaCl is present in 2000 mL of M NaCl solution?
1 L
1000 mL
0.225 moles NaCl
1 L solution
2000 mL soln x x =
0.450 moles
Or…
0.225 moles NaCl
1000 mL solution
2000 mL soln x =
0.450 moles NaCl

52. Solution Concentrations
Using the concentration as a conversion factor:
What volume of M NaCl solution will contain moles of dissolved NaCl?
1 L
0.225 Moles
1000 mL
1 L
moles x x =
77.8 mL
Or…
1000 mL solution
0.225 moles NaCl
moles NaCl x =
77.8 mL soln

53. Solution Stoichiometry
Just as grams of a pure substance and its FW determine moles of the substance, so do volulme and molarity of a substance in its solution.
As for “pure substance” stoichiometry, solution stoichiometry usually involves a three-step approach:

54. Solution Stoichiometry
Consider reaction of M HCl with sodium carbonate:
2HCl Na2CO3  2NaCl CO2 + H2O
25.0 mL
? g
Use volume and
HCl molarity
Use moles and
FW of Na2CO3
? moles
? moles
Use Equation
Coefficients
How many grams of Na2CO3 will react with mL of M HCl solution?

55. Solution Stoichiometry
Consider reaction of M HCl with sodium carbonate:
2HCl Na2CO3  2NaCl CO2 + H2O
25.0 mL
? g
Use volume and
HCl molarity
Use moles and
FW of Na2CO3
? moles
? moles
Use Equation
Coefficients
1000 mL HCl
0.200 mole HCl
2 mole HCl
1 mole Na2CO3
106 g Na2CO3
1 mole Na2CO3
25.0 mL HCl x x x
= grams Na2CO3

56. Solution Stoichiometry
Consider reaction of M HCl with sodium carbonate:
2HCl Na2CO3  2NaCl CO2 + H2O
? mL
5.00 g
Use moles and
HCl molarity
Use grams and FW
? moles
? moles
Use Equation
Coefficients
What volume of M HCl solution is required for reaction with 5.00 grams of Na2CO3?

57. Solution Stoichiometry
Consider reaction of M HCl with sodium carbonate:
2HCl Na2CO3  2NaCl CO2 + H2O
? mL
5.00 g
Use moles and
HCl molarity
Use grams and FW
? moles
? moles
Use Equation
Coefficients
106 g Na2CO3
1 mole Na2CO3
1 mole Na2CO3
2 mole HCl
0.200 mole HCl
1000 mL HCl
5.00g Na2CO3 x x x
= 472 mL HCl solution

58. Solutions vs Colloids Solution Colloids
Solute particle are of ionic or molecular size (a few nm across)
Transparent to ordinary light
Stable unless solvent evaporated
Colloids
Solute (called “dispersed phase”) typically 1000 nm or more per particle
Giant molecules (or “clumps” of smaller ones)
Not totally transparent – Tyndall Effect
Dispersed phase may separate out (similar to separation of mayonnaise).

59. Solutions vs Colloids The Tyndall Effect True Solution Colloidal
Mixture

60. Solutions vs Colloids The Tyndall Effect True Solution Colloidal
Mixture

61. Transmembrane Diffusion
Solution
(H2O +
Solutes)
Pure
H2O
Semipermeable membrane
Only water passes through osmotic membranes and faster from the side on which water is more concentrated.

62. Transmembrane Diffusion
Solution
(H2O +
Solutes)
Pure
H2O
Semipermeable membrane
Diffusion rates tend to equalize as flow continues.

64. Osmotic Pressure
If applied pressure is too low, H2O flows into the region of higher solute concentration...
“Down the concentration gradient” for H2O. P P
Membrane
Pure H2O
H2O +
Solutes

65. Osmotic Pressure P
If applied pressure is too high, H2O flows into the region of lower solute concentration...
Against the natural concentration gradient for H2O.
--Reverse Osmosis P
Membrane
Pure H2O
H2O +
Solutes

66. Osmotic Pressure P
Minimum pressure required to maintain equal flow rates (to prevent infusion of H2O).
Proportional to solute concentration differences across membrane. P
Membrane
Pure H2O
H2O +
Solutes

67. Solutions vs Colloids Solution
Solute particles are of ionic or molecular size
Transparent to ordinary light
Stable unless solvent evaporated
May pass through dialytic, but not true osmotic, membranes
Colloids
Typically 1000 nm or more per particle
Not totally transparent – Tyndall Effect
May separate out
Particles too large to pass through most membranes

68. Transmembrane Diffusion
Mixture
(H2O,
Na+Cl-,
protein)
H2O
NaCl more concen-trated here
Pure
H2O
NaCl
H2O more concentrated here
Dialytic membrane
Water and solutes pass down concentration gradient through dialytic membrane. Colloids do not cross membrane.

69. Solution Concentrations
Expressed as a ratio of the amount of solute to the total amount of solution:
Osmoles (total moles)
Amount of solute
Concentration =
Total amount of solution
( Osmolarity, osM)
Liters
For certain solutes, osM will equal M.

70. Osmolarity Calculating Impact
Total of molarities of all types of solute particles in the solution.
For ionic solutes, the ions are separated; and each ion has a separate molarity to be totaled.
Molecular solutes have same molarity and osmolarity, but each different solute needs to be included.
Impact
Osmolarity determines osmotic pressure
Useful in determining net direction of H2O flow across membranes.

71. Osmolarity Solute, M Osmolarity 0. 25-M C6H12O6 (molecular) 0. 25-osM
0. 25-M NaCl (ionic)
0. 50-osM
(0.25-M Na M Cl-)
0. 10-M CaBr2 (ionic)
0. 30-osM
(0.10-M Ca M Br-)
0. 25-osM
(0.10-M Fe M SO42-)
0. 05-M Fe2(SO4)3 (ionic)

72. Transmembrane Diffusion
Dialytic membrane
0.6 osM
+ 1% colloid
1.0 osM
+ 2% colloid A B
H2O
Cl-
0.2 osM
Ca2+
C6H12O6
0.2 osM
0.6 osM
0.1-M NaCl
0.1-M CaCl2
0.1-M C6H12O6
1% starch
0.1-M NaCl
0.2-M CaCl2
0.2-M C6H12O6
2% starch
0.3 osM
0.2 osM
0.1 osM

73. Transmembrane Diffusion
Dialytic membrane
0.6 osM
+ 1% colloid
1.0 osM
+ 2% colloid A B
H2O
Cl-
Hypotonic
Hypertonic
Ca2+
C6H12O6
0.1-M NaCl
0.1-M CaCl2
0.1-M C6H12O6
1% starch
0.1-M NaCl
0.2-M CaCl2
0.2-M C6H12O6
2% starch
Water flows into hypertonic fluid (where water is less concentrated).

74. Transmembrane Diffusion
Arterial End
“Head pressure” --High
Venous End
“Head pressure” --Low
Tissue Cell
Wastes
Head pressure of heart “pushes” nutrients and water into cell (PBLOOD> POSMOTIC).
Nutrients
Hypertonic blood “draws” wastes into blood (POSMOTIC>PBLOOD) .

75. Solution Concentrations
4.75 grams of NaCl is dissolved in sufficient water to make 750 mL of solution.
What is the % (w/v) concentration of this solution?
0.633%
NaCl
The concentration is % (w/v).
750 mL