1
Chapter 8
Gas
Solutions
Liquid
Solid
2
Ch 8.1 Characteristics of Solutions
A solution is a ________________ mixture
• Two or more substances; each retains its own
identity
• Composition can vary
• Properties can vary with ____________
• Uniform properties throughout
• One visible phase
• Can be separated by ___________ means
3
Solvent
__________ quantity
same phase as solution
Solute
__________ quantity
material dissolved in solvent
Figure 8.1 colored crystals (solute) dissolve in clear
liquid (solvent) to produce a solution.
4
Ch 8.2 Solubility is the maximum amount of solute
that will dissolve in a given amount of solvent under
a given set of conditions.
Factors affecting solubility
•
•
•
•
___________ of solute & solvent
Temperature
Pressure (in case of gases)
Presence of other _________
5
Most solids become
________ soluble
in water with
increasing
temperature.
Table 8.1
6
The solubility of a gas in water ____________ with
increasing temperature.
Fish kill as a result of
oxygen depletion.
7
Effect of Pressure on Solubility of Gases
Henry’s Law
The amount of a gas that will
dissolve in a liquid at a given
temperature is directly proportional
to the ___________ pressure of the
gas above the liquid.
William Henry
1775-1836
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The larger oxygen partial pressure in an oxygen-enriched
mixture translates into increased oxygen uptake.
9
Decompression Sickness (divers' disease, the bends or caisson
disease) describes a condition arising from dissolved gases coming
out of solution into bubbles inside the body on depressurization.
Most commonly a type of scuba diving hazard but may be
experienced in caisson
working, flying in
unpressurised aircraft,
and extra-vehicular
activity from spacecraft.
Scuba divers making a
decompression stop
Decompression chambers.
10
A saturated solution contains the _________
amount of solute that can be dissolved under
a given set of conditions.
Figure 8.3
In a saturated solution, the
dissolved solute is in
dynamic equilibrium with
undissolved solute.
Example:
dissociation
NaCl(s) + H2O(l)
____________
Na+(aq) + Cl-(aq)
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A supersaturated solution is an unstable solution that
temporarily contains more dissolved solute than that
present in a
saturated solution.
It will produce
crystals rapidly,
often in a dramatic
manner, if it is
slightly disturbed
or if it is “______”
with a tiny crystal
of solute.
12
Unsaturated solution
• contains ________ than the maximum
amount of solute
Concentrated solution
• contains a large amount of solute relative
to the amount that could dissolve
Dilute solution
• contains a _______ amount of solute
relative to the amount that could dissolve
13
Ch 8.3 Solution Formation
Fig. 8.5 An ionic compound dissolves in H2O to form _______ ions.
14
Energy is needed to overcome ____________ forces:
• Attraction between solute particles (ionic bonds
for ionic compounds)
• Attraction between solvent particles (hydrogenbonding for water molecules)
Energy is released from the solvation of the ions.
The overall process can be exothermic or
____________.
Instant Cold Pack
NH4NO3 + H2O
Endothermic
Instant Hot Pack
CaCl2 or MgSO4 +
H2O
______________
15
Supplemental material: Entropy
The universe has a tendency to move towards disorder.
Throw a deck of cards and they will fall in a disorderly
heap, not assembled according to suit. When disorder
increases, we say entropy ___________.
16
When salts dissolve in water, disorder/entropy __________.
Salts that dissolve in an endothermic process (such as in the Instant
Cold Pack) do so because the change in entropy is sufficiently
favorable to counterbalance the unfavorable change in enthalpy
(heat of solution).
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Ch 8.4 Solubility Rules
A. Gases mix with each other in all proportions.
Neither liquids nor solids can be solutes in air.
Fog and smoke are colloids, not ___________.
B. Ionic solutes in water
Table 8.2
Solubility guidelines for ionic compounds in water.
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C. Molecules as solute and solvent
The generalization “_________________” is a good tool to
predict solubility behavior when molecules are involved.
Water, which is a polar
solvent, is a good solvent
for polar solutes, ionic
compounds, and
substances that produce
ions in water. It is not a
good solvent for nonpolar
molecules.
Oil and H2O
have different _________
and are relatively
insoluble in each other.
Figure 8.6
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Molecules that mix in all proportions are miscible.
CH3CH2-OH + H2O are miscible because of
____________________.
20
Compared to ethanol, n-hexanol’s solubility in water
is much lower (0.59g/100mL at 20oC) because of its
long hydrocarbon chain.
CH3-CH2-CH2-CH2-CH2-CH2-OH
Hydro______ portion (nonpolar),
no interaction with water
Hydro______
polar & attracted
to water
21
Sodium stearate has an 18-carbon, hydrophobic ____
and a charged hydrophilic _______ group.
It forms micelles in
aqueous solution
and is the major
component of
soaps along with
many types of solid
deodorants,
rubbers, latex
paints, inks.
A typical micelle in aqueous solution. The hydrophobic head
groups are in contact with water, sequestering the hydrophobic
single tails in the micelle center.
22
Nonpolar solvents, will readily dissolve _________ solutes.
Fat-soluble vitamins (A, D, E, K), for example, have
nonpolar structures that are compatible with the nonpolar
nature of fats.
The hydrophobic character of the fat-soluble vitamins
determines their _____________.
23
Drill problem. Name the following molecules and
predict which will dissolve in H2O. Explain your
predictions.
NH3
CH4
CCl4
LiNO3
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Ch 8.5 Solution Concentration Units
Percent Concentration
% by mass =
mass of solute
x 100
total mass of solution
mass of solution = mass solute + mass solvent
units are usually in grams and abbreviated as % (m/m)
or w/w %
Sample calculation: What is the w/w % of a solution
prepared by dissolving 6.4 g NaCl in 100.0 g water?
x 100 = 6.4g NaCl
x 100
6.4g NaCl
6.4g NaCl + ____ g H2O
______g solution
= ______ % NaCl
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% by volume =
volume of solute x 100
volume of solution
units are usually in mL and abbreviated as % (v/v)
A 5% (v/v) alcohol-in-water solution contains 5.0 mL
of alcohol ___________ to a total volume of 100 mL
with water.
26
When volumes of two different liquids are combined, the
volumes are not _____________.
Figure 8.7
The combined
volumes or alcohol and water
are less than the sum of the
individual volumes.
Figure 8.8
50 mL alcohol + 50 mL water
= _________ mL solution
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Percent by volume is the commonly used unit on labels of
alcohol-containing products. Many countries also use a
measure called a standard drink. In the USA, it is any drink
that contains about 14 g of pure alcohol, which is thought
to be the amount that an average liver can metabolize in
one hour. The purpose of the standard drink measure is to
help drinkers monitor and control their alcohol intake.
Sample calculation: How many ounces of wine (12 % v/v)
are in one standard drink?
12 mL pure alcohol in 100 mL wine
Density of pure alcohol = 0.789 g/mL
1 ounce = ______ mL
g alcohol → mL alcohol →
mL wine → ounces wine
14 g alcohol
x 1 mL x 100 mL wine x 1 oz .
1 standard drink 0.789 g
12 mL alcohol
____ mL
= _______ oz of wine/standard drink
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Examples of one standard drink:
40%
12%
5% (v/v)
Proof (a standard of alcohol strength) = 2 x % (v/v)
Historically, proof was defined as the most dilute spirit that would sustain
combustion of gunpowder (57.15 % v/v).
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Mass-Volume %
=
mass of solute (g)
x 100
volume of solution (mL)
The units are specified in grams and mL because they
___________. The abbreviation is % (m/v) or w/v %.
Normal saline is the commonlyused term for a solution of 0.9 %
w/v of NaCl. It contains 0.9 g
NaCl in 100 mL of aqueous
solution.
Sample calculation: How many
grams of NaCl are present in 1.0 L
of normal saline solution?
1.0 L soln x 103 mL x 0.9 g NaCl = _____ NaCl
1L
100 mL soln
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Parts-per notation is used when
particularly low concentrations are involved.
Supplemental material:
Parts-per-million
ppm = mass or volume of solute
x 106
mass or volume of solution
ppb parts-per-billion, 1 part in ______
ppt parts-per-trillion, 1 part in ______
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Chemists prefer to use the concentration unit of Molarity.
Molarity (M) = moles of solute
L of solution
Sample calculation: How many grams of solute are
contained in ___ L of 0.10 M KCl? (F.W. 74.55 amu)
L KCl solution →
mol KCl
→
g KCl
___ L x 0.10 mole KCl x 74.55 g KCl = __ g KCl
L
mol
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Drill problem:
A particular reaction requires ______ g Ca2+. What
volume of 2.0 M CaCl2 is needed to provide that
amount?
g Ca2+ → mol Ca2+ → mol CaCl2 → volume soln
_____ Ca2+ x 1 mol x
40.1 g
= 0.024 L or
24 mL
1 mol CaCl2
1 mol Ca2+
x
1L
.
2.0 mol CaCl2
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Ch 8.6 Dilution
Figure 8.9 Frozen orange juice
concentrate is diluted with water
prior to drinking.
Figure 8.4 Both solutions
contain the _________
amount of solute.
concentrated
stock solution
dilute solution
A simple relationship exists between the concentrations (C)
and volumes (V) of the two solutions (soln).
Cstock soln x Vstock soln = Cdilute soln x Vdilute soln
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Practice calculation. If 50 mL of a stock solution of 1.0 M
KBr are diluted to a volume of 1.0 L, what will be the final
concentration of the dilute solution of KBr?
Cs x Vs = Cd x Vd
(you must know this equation)
1.0 M x 50 mL = Cd x _______
units must cancel
Cd = _________ M KBr
This is a 20-fold dilution of the stock solution.
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Practice problem: How much water must be added to
100 mL of ____ M NaCl to prepare a 0.0500 M NaCl
solution?
Cs x Vs = Cd x Vd
(you must know this equation)
_____ M x 100 mL = 0.0500 M x Vd
Vd = 600 mL = final volume (Vs + Vwater)
Vwater
= Vd – Vs
= 600 mL – 100 mL
= 500 mL
Q: How many-fold of a dilution has occurred?
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Ch 8.7 Colloidal Dispersions and Suspensions
Milk is NOT a solution but a
________________.
Colloidal
dispersions
_________
light
(Tyndall
effect), true
solutions do
not.
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Table 8.4 Property comparison for solutions, colloidal dispersions,
and suspensions.
Examples of Colloids
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Ch 8.8 Colligative Properties of Solutions are
properties that depend on the number of solute
particles in solution, not on their ___________.
•
•
•
•
reduction of vapor pressure
elevation of boiling point
depression of freezing point
osmotic pressure
The magnitude of a colligative property is directly
proportional to the total concentration of _____ the species
formed when solutes dissolve.
Example. When 1 mole of CaCl2 and 1 mole of sugar are
dissolved together in water, we have a total of 4 moles of particles:
1 mole CaCl2 → 1 mole Ca2+ + 2 moles Cl+ 1 mole sugar → 1 mole of molecules
.
____ moles of particles
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Figure 8.11 Effect of a ____________ solute on the vapor
pressure of a solvent.
pure solvent
solution
Fewer solvent molecules escape from the solution, resulting
in a reduction of the vapor pressure.
The greater the concentration of solute particles, the _____
will be the reduction in the vapor pressure.
40
Higher temperatures are needed to raise the depressed
vapor pressure of a solution to the boiling point →
elevation of the boiling point.
An increase in the b.p. of a solvent is directly proportional
to the concentration of solute particles.
Example: The boiling point of water increases by 0.52oC
per mole of solute particles per kilogram of water. If the
solute is 1 mole of sugar, the boiling point of the aqueous
solution is _________oC.
Q: What will be the b.p. if the solute is 1 mole of NaCl?
41
Figure 8.12 A water-antifreeze
mixture has a higher boiling
point AND a ________ freezing
point than pure water. The
depression of the freezing point
due to solutes is directly
proportional to the total
concentration of all the particles
dissolved.
NaCl/ice 1:3 –20oC
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Freezing Point Depression at the Molecular Level.
Melting
Ice
Solution
Freezing
At equilibrium: rate of melting = rate of freezing
When the rate of freezing of solvent molecules decreases in
the presence of solute particles, then the rate of melting
must also decrease to establish a new equilibrium. For this
to happen, the temperature (m.p. of the solution) must ____.
43
Ch 8.9 Osmosis and Osmotic Pressure
Fig. 8.13 Osmosis is the flow of solvent through a semipermeable
membrane from a ______ solution to a more __________ solution.
(b) The liquid level rises until equilibrium is reached. At equilibrium, the
solvent molecules move back and froth across the membrane at equal rates.
44
Figure 8.14 Osmosis at the molecular level.
Solute molecules literally interfere with the movement of
solvent molecules across the membrane.
45
Figure 8.15 Osmotic pressure is
the amount of pressure needed to
________ the net flow of solvent
across the membrane in the
direction of the more concentrated
solution.
The greater the difference in
concentrations between the
separated solutions, the ________
the magnitude of the osmotic
pressure.
46
Reverse osmosis is used in the desalination of
seawater to make drinking water.
47
13,080 Desalination plants
world-wide produce more
than 12 ________ gallons of
water a day (according to the
International Desalination Association).
Reverse osmosis desalination plant in
Barcelona, Spain
48
Cell membranes in both
plants and animals are
semipermeable in nature.
Figure 8.16 The dissolved
substances in tree sap
create a more concentrated
solution than the
surrounding ground water.
Water enters membranes in
the roots and rises in the
tree, creating an osmotic
pressure that can exceed 20
atm in extremely tall trees.
49
The concentration of solute particles is called osmolarity.
It is distinct from molarity because it measures moles of
solute particles rather than __________ of solute.
osmolarity = molarity x i
i = number of particles produced from the dissociation of
one formula unit of solute
What is the osmolarity of a solution that is 1 M in
MgBr2 and 2 M in glucose?
Example:
Osmolarity = 1 M x 3 + 2 M x 1 = __________
MgBr2
glucose
50
The osmotic pressure of a solution is directly
proportional to the number of solute particles present.
Solution A
0.30 osmol = 7.6 atm
Solution B
0.15 osmol = 3.8 atm
Solution C
1.5 osmol = ?
The relationship between osmotic pressure (∏) and the
osmolarity of the solute particles resembles the ________
gas law:
∏V = nRT
n = number of moles of all solute particles
R = universal gas constant
51
Isotonic, Hypotonic, and Hypertonic solutions pertain to
osmotic-type of phenomena that occur in the human body.
Fig 8.17 Effects of bathing red blood
cells in various types of solutions.
A red blood cell in a physiological
saline solution (____ tonic solution).
In pure water (______tonic solution)
the red blood cell swells and
hemolysis occurs.
Shrinking or crenation occurs
in a concentrated NaCl
solution (_______tonic
solution).
52
Ch 8.10 Dialysis is a process in which a semipermeable
membrane allows the passage of solvent, dissolved ions,
and small molecules, but blocks the passage of larger
particles.
Before
After
Figure 8.18 In dialysis there is a ______ movement of ions.
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Figure 8.19 Impurities (ions)
can be removed from a colloidal
dispersion by using a dialysis
procedure.
The Artificial Kidney
Hemodialysis Machine