Solutions and Colloids
Homogeneous (or nearly
homogeneous) Mixtures
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
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.

Water
O
H
“H-bonding”
binds water
molecules
tightly.
H
H
O
H
O
H
H
O
H
H
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

Water
Crystal’s +/- attractions cause
lattice energy, which must be
overcome to break up crystal.
Na+
Cl-
Water
Na+
Cl-
Water
“Void” weakens
crystal and makes it
more likely to break
up in vicinity.
Several more H2O
molecules may
associate
Na+
Cl-
Water
Na+
Cl-
Water
Na+
Cl-
Water
Note: Positive ions associate
with negative ends of waters,
and negative ions associate with
positive ends of waters.
Na+
Cl-
+/- forces
release
energy
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.
Water
Water
An exothermic dissolving process.
Hydration energy is greater than
lattice energy.
Water
Water
An endothermic dissolving process.
Lattice energy is greater than
hydration energy.
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.
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.
Solution Concentrations
20 gal.
.
Solution Concentrations
.
Dilute or Concentrated???
Solution Concentrations
.
Dilute or Concentrated???
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???
Solution Concentrations
Expressed as a ratio of the amount of solute
to the total amount of solution:
grams
Concentration =
(%, w/v)
Amount of solute
Total amount of solution
mL
Solution Concentrations
Expressed as a ratio of the amount of solute
to the total amount of solution:
mass (grams)
Concentration =
(%, w/w)
Amount of solute
Total amount of solution
mass unit
(grams)
Solution Concentrations
Expressed as a ratio of the amount of solute
to the total amount of solution:
mg
Concentration =
( mg %)
Amount of solute
Total amount of solution
dL
Solution Concentrations
Expressed as a ratio of the amount of solute
to the total amount of solution:
moles
Concentration =
( molarity, M)
Amount of solute
Total amount of solution
Liters
Solution Concentrations
% Concentration has multiplier of 100 to
place ratio on “parts per 100” basis:
%, w/v =
Grams of solute
mL of solution
X 100
Solution Concentrations
‰ Concentration has multiplier of 1000 to
place ratio on “parts per 1000 total” basis:
‰=
Grams of solute
mL of solution
X 1000
Solution Concentrations
ppm concentration has multiplier of 106 to
place ratio on “parts per million total” basis:
ppm
Grams of solute
=
mL of solution
X 106
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?
%, w/v =
%=
Grams of solute
mL of solution
4.75 g
750 mL
X 100
X 100 = 0.633 %
The g/mL units are understood but not included.
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?
The concentration
is 0.633 % (w/v).
0.633%
NaCl
750 mL
Solution Concentrations
Another:
12.5 grams of H2SO4 is dissolved in sufficient water to
make 0.500 liters of solution.
What is the % (w/v) concentration of this solution?
Grams of solute
X 100
%, w/v =
mL of solution
Solution volume units must be converted from liters to
12.5 g
X 100
mL before
0.500
L = 500
% =doing calculations:
= 2.50
% mL.
500 mL
The g/mL units are understood but not included.
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
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
or
100 mL solution
0.85 g NaCl
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?
How much dissolved NaCl is
in this 2000 mL of saline
solution?
0.85%
NaCl
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
2000 mL soln X
100 mL solution
= 17.0 g NaCl
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?
17.0 grams of dissolved NaCl
is present in 2000 mL of this
solution
0.85%
NaCl
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?
What volume will contain
2.50 grams of dissolved
NaCl?
0.85%
NaCl
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?
2.50 g NaCl
100 mL solution
X
0.85 g NaCl
= 294 mL soln
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?
294 mL of this solution
contains 2.50 grams of
dissolved NaCl.
0.85%
NaCl
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.

Solution Concentrations
Three types of calculations dealing with
concentrations:
2
Concentration =
1
Amount of solute
Total amount of solution
3
Solution Concentrations
Given any two, be able to calculate the
third:
2
Concentration =
1
Amount of solute
Total amount of solution
3
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?
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.
Solution Concentrations
Molarity
Moles of solute
Liters of solution
M=
4.75 grams of NaCl is dissolved in sufficient water to
make 750 mL of solution. M = ?
4.75 g NaCl X
750 mL
X
1 mole NaCl
58.5 g NaCl
= 0.0812 mole NaCl
1 Liter
1000 mL
= 0.750 L
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
M=
0.0812 moles NaCl
0.750 Liters of solution
0.0812 mole NaCl
= 0.108 M NaCl
= 0.108 moles NaCl/L
0.750 L
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?
The concentration
is 0.633 % (w/v)
and…
is 0.108 M
0.633%
0.108 M
NaCl
750 mL
Solution Concentrations
Given any two, be able to calculate the
third:
2
Concentration =
1
Amount of solute
Total amount of solution
3
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 0.225-M NaCl solution?
How much dissolved NaCl is
in this 2000 mL of saline
solution?
0.225M
NaCl
Solution Concentrations
Using the concentration as a conversion
factor:
How many moles of NaCl is present in 2000 mL
of 0.225-M NaCl solution?
0.225 moles NaCl
1L
x
2000 mL soln x
= 0.450 moles
1000 mL
1 L solution
Or…
0.225 moles NaCl
2000 mL soln x
1000 mL solution
= 0.450 moles NaCl
Solution Concentrations
Using the concentration as a conversion
factor:
What volume of 0.225-M NaCl solution will
contain 0.0175 moles of dissolved NaCl?
0.0175 moles x
1L
x 1000 mL = 77.8 mL
0.225 Moles 1 L
Or…
1000 mL solution
= 77.8 mL soln
0.0175 moles NaCl x
0.225 moles NaCl
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:

Solution Stoichiometry
Consider reaction of 0.200-M HCl with sodium carbonate:
2HCl + Na2CO3  2NaCl + CO2 + H2O
?g
25.0 mL
Use volume and
HCl molarity
? moles
Use moles and
FW of Na2CO3
? moles
Use Equation
Coefficients
How many grams of Na2CO3 will react with 25.0
mL of 0.200-M HCl solution?
Solution Stoichiometry
Consider reaction of 0.200-M HCl with sodium carbonate:
2HCl + Na2CO3  2NaCl + CO2 + H2O
?g
25.0 mL
Use volume and
HCl molarity
? moles
Use moles and
FW of Na2CO3
? moles
Use Equation
Coefficients
0.200 mole HCl x 1 mole Na2CO3 x
25.0 mL HCl x
2 mole HCl
1000 mL HCl
= 0.265 grams Na2CO3
106 g Na2CO3
1 mole Na2CO3
Solution Stoichiometry
Consider reaction of 0.200-M HCl with sodium carbonate:
2HCl + Na2CO3  2NaCl + CO2 + H2O
? mL
5.00 g
Use moles and
HCl molarity
Use grams and FW
? molesUse Equation
? moles
Coefficients
What volume of 0.200-M HCl solution is required
for reaction with 5.00 grams of Na2CO3?
Solution Stoichiometry
Consider reaction of 0.200-M HCl with sodium carbonate:
2HCl + Na2CO3  2NaCl + CO2 + H2O
? mL
5.00 g
Use moles and
HCl molarity
? moles
Use grams and FW
? moles
Use Equation
Coefficients
1 mole Na2CO3 x 2 mole HCl
x 1000 mL HCl
5.00g Na2CO3 x
0.200 mole HCl
1 mole Na2CO3
106 g Na2CO3
= 472 mL HCl solution
Solutions vs Colloids

Solution
– 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).
Solutions vs Colloids
The Tyndall Effect
True
Solution
Colloidal
Mixture
Solutions vs Colloids
The Tyndall Effect
True
Solution
Colloidal
Mixture
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.
Transmembrane Diffusion
Solution
(H2O +
Solutes)
Pure
H2O
Semipermeable membrane
Diffusion rates tend to equalize as flow continues.
Osmotic Pressure
P
P
“Down the
concentration
gradient” for
H2O.
Membrane
H2O +
Solutes
If applied
pressure is too
low, H2O flows
into the region
of higher solute
concentration...
Pure
H2O
Osmotic Pressure
P
P
Membrane
H2O +
Solutes
Pure
H2O
If applied
pressure is too
high, H2O flows
into the region
of lower solute
concentration...
Against the
natural
concentration
gradient for
H2O.
--Reverse
Osmosis
Osmotic Pressure
P
P
Membrane
H2O +
Solutes
Pure
H2O
Minimum
pressure
required to
maintain equal
flow rates (to
prevent infusion
of H2O).
Proportional to
solute
concentration
differences
across
membrane.
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
Transmembrane Diffusion
NaCl
more
concentrated
here
Mixture H2O
(H2O,
NaCl
+
Na Cl ,
protein)
Pure
H2O
Dialytic membrane
H2O more
concentrated
here
Water and solutes pass down concentration gradient through
dialytic membrane. Colloids do not cross membrane.
Solution Concentrations
Expressed as a ratio of the amount of solute
to the total amount of solution:
Osmoles
(total moles)
Concentration =
Amount of solute
Total amount of solution
( Osmolarity, osM)
Liters
For certain solutes, osM will equal M.
Osmolarity

Calculating
– 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.
Osmolarity
Solute, M
Osmolarity
0. 25-M C6H12O6 (molecular) 0. 25-osM
0. 25-M NaCl (ionic)
0. 50-osM
(0.25-M Na+ + 0.25-M Cl-)
0. 10-M CaBr2 (ionic)
0. 30-osM
(0.10-M Ca+ + 0.20-M Br-)
0. 05-M Fe2(SO4)3 (ionic)
0. 25-osM
(0.10-M Fe3+ + 0.15-M SO42-)
Transmembrane Diffusion
Dialytic membrane
1.0 osM
+ 2%
colloid
0.2 osM
0.6 osM
0.1-M NaCl
0.2-M CaCl2
0.2-M C6H12O6
2% starch
A
H2O
B
ClCa2+
0.6 osM
+ 1%
colloid
0.2 osM
C6H12O6
0.3 osM
0.2 osM
0.1 osM
0.1-M NaCl
0.1-M CaCl2
0.1-M C6H12O6
1% starch
Transmembrane Diffusion
Dialytic membrane
1.0 osM
+ 2%
colloid
Hypertonic
0.1-M NaCl
0.2-M CaCl2
0.2-M C6H12O6
2% starch
A
H2O
B
ClCa2+
C6H12O6
Water flows into
hypertonic fluid
(where water is
less concentrated).
0.6 osM
+ 1%
colloid
Hypotonic
0.1-M NaCl
0.1-M CaCl2
0.1-M C6H12O6
1% starch
Transmembrane Diffusion
Tissue Cell
“Head
pressure” -Low
Venous End
Arterial End
“Head
pressure” -High
Wastes
Nutrients
Head pressure of heart
“pushes” nutrients and
water into cell (PBLOOD>
POSMOTIC).
Hypertonic blood “draws”
wastes into blood
(POSMOTIC>PBLOOD) .
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?
The concentration
is 0.633 % (w/v).
0.633%
NaCl
750 mL