Transcript Photo chapter opener 17 The left beaker contains copper sulfate

Properties of
Solutions
The left beaker contains copper sulfate solution.
In the right beaker, ammonia is being added to create a
precipitate of copper(II) hydroxide.
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17a–2
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17a–3
Figure 17.1: The formation of a liquid
solution can be divided into three steps
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17a–4
Figure 17.2: (a) Enthalpy of solution Hsoln has a negative sign (the process is
exothermic) if Step 3 releases more energy than is required by Steps 1 and 2.
(b) Hsoln has a positive sign (the process is endothermic) if Stpes 1 and 2 require
more energy than is released in Step 3.
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17a–5
French Navy ship L'Ailette equipped with
vacuum pumps approaches an oil slick.
Source: AP/Wide World Photos
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17a–6
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17a–7
Multistage
supercritic
al fluid
extraction
apparatus
Source: USDA
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17a–8
Chicken fat obtained by using supercritical
carbon dioxide as the extracting agent.
Source: USDA
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17a–9
“Likes Dissolve Likes”
• substances with similar noncovalent forces
are likely to be soluble in each other
• solutes do not readily dissolve in solvents
whose noncovalent forces are quite different
from their own
• stronger solute-solvent attractions favor
solubility, stronger solute-solute or solventsolvent attractions reduce solubility
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17a–10
Solubilities
of Some
Alcohol
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17a–11
Solution Terminology
saturated
• solution containing undissolved solute in
equilibrium with the solution
unsaturated
• solution containing less than the maximum
amount of solute
supersaturated
• solution containing more solute than is
normally allowed
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Types of Solutions
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17a–13
Supersaturated Solution
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17a–14
Carbonation in a bottle of soda
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17a–15
Figure 17.4: (a) a gaseous solute in equilibrium with a solution.
(b) the piston is pushed in, which increases the pressure of the gas
and the number of gas molecules per unit volume. (c) greater gas
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17a–16
Henry's Law
The solubility of a gas in a liquid depends on
temperature, the partial pressure of the gas over the
liquid, the nature of the solvent and the nature of the
gas.
Low pressure
Low concentration
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Double the pressure
equilibrium
Double the concentration
17a–17
Cuba diving with trimix
trimix= oxygen, nitrogen and helium
Why one should dive deep dives with trimix?
1. Nitrogen narcosis can be avoided by replacing nitrogen with helium.
Helium is not as narcotic as nitrogen.
2. By decreasing the percentage of oxygen in the mix, one can dive
deeper without a danger of oxygen toxicity.
•Disadvantages of Helium:
•The best known effect of helium is its distortion of speech.
The thinner gas passing across the vocal cords at atmospheric
pressure produces a comical high-pitched squeak reminiscent
of Donald Duck and family.
•There is an apparent chilling during breathing.
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17a–18
Henry’s Law
Sg = kHPg
where Sg  solubility
kH  Henry’s
Law constant
Pg  partial
pressure
of gas
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17a–19
Henry’s Law
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17a–20
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17a–21
Figure 17.6:
The solubilities
of several
gases in water
as a function of
temperature at
a constant
pressure of
1 atm of gas
above the
solution.
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17a–22
Solubility of Oxygen in Water
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17a–23
Lake Nyos in Cameroon
The stability of such a "time bomb" stems from the fact that CO2-rich
waterCorbis
is denser than pure water, as long as gas bubbles do not
Source:
nucleate.
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17a–24
Figure 17.5: The solubilities of several
solids as a function of temperature.
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17a–25
Solubility of Ionic
Compounds and
Temperature
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17a–26
Water Dissolving An Ionic Solute
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17a–27
Hydration of a Sodium Ion
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17a–28
Comparison of Concentration Terms
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17a–29
Parts per Million
#g of solute
#mg of solute
 106 =
ppm =
#g of solution
#micro-L solute
ppm =
#Lof solution
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#kg of solution
Parts per Billion
#g of solute
ppb =
#g of solution
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 109 =
#micro-g of solute
#kg of solution
Figure 17.7: Pipe with accumulated mineral
deposits (left) lengthwise section (right)
Source: Visuals Unlimited
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17a–32
Figure 17.8: An aqueous solution and pure
water in a closed environment
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17a–33
Figure 17.9: The presence of a nonvolatile solute inhibits
the escape of solvent molecules from the liquid
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17a–34
Figure 17.10: For a solution that obeys Raoult’s law,
a plot of Psoln versus xsolvent yields a straight line.
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17a–35
Colligative Properties
• properties that depend on the number of
particles not on the identity of the particles
Raoult’s Law
P1 = X1P1o
• vapor pressure lowering
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17a–36
Vapor Pressure of
Pure Water vs. Sea Water
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17a–37
Figure 17.11: Vapor pressure for a solution
of two volatile liquids.
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17a–38
Solvent Freezing
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17a–39
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17a–40
Figure 17.13: Ice in equilibrium with
liquid water.
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17a–41
Figure 17.12: Phase diagrams for pure water (red lines)
and for an aqueous solution containing a nonvolatile
solution (blue lines).
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17a–42
Boiling Point Elevation
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17a–43
Boiling Point Elevation
DT = Tfinal - Tinitial
(DTb = bpsolution - bppure solvent)
DTb = kb x m
where kb => boiling point elevation constant
m => molality of all solutes in solution
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Freezing Point Depression
DT = Tfinal - Tinitial
(DTf = fppure solvent - fpsolution)
DTf = kf x m
where kf => freezing point depression
constant
m => molality of all solutes in solution
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Figure 17.14: A tub with a bulb on the end is
covered by a semipermeable membrane.
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17a–46
Figure 17.15: The normal flow of solvent into
the solution (osmosis) can be prevented by
applying an external pressure to the solution.
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17a–47
Figure 17.16: A pure solvent and its solution (containing a nonvolative
solute) are separated by a semipermeable membrane through which
solvent molecules (blue) can pass but solute molecules (green) cannot.
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17a–48
Osmosis
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17a–49
Osmotic Pressure
P = cRTi
where P => osmotic pressure
c => concentration
R => gas constant
T => absolute temperature
i => number of particles per
formula
unit
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17a–50
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17a–51
Figure 17.17: Representation of the
functioning of an artificial kidney
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17a–52
Figure 17.18: Reverse osmosis
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17a–53
Family uses a commercially available desalinator,
similar to those developed by the Navy for life rafts.
Source: Recovery Engineering, Inc.
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17a–54
Figure 17.20: Residents of Catalina Island off the coast of southern
California are benefiting from a desalination plant that can supply
132,000 gallons of drinkable water per day, one-third of the island's daily needs.
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17a–55
Colligative Properties
of Electrolytes
vpwater > vp1M sucrose > vp1M NaCl > vp 1M CaCl2
1 mole sucrose = 1 mole molecules
1 mole NaCl = 2 mole of ions
1 mole CaCl2 = 3 moles ions
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17a–56
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17a–57
Figure 17.21: In a aqueous solution a few ions
aggregate, forming ion pairs that behave as a unit.
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17a–58