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“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 solvent-solvent attractions reduce solubility
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Solution Terminology
saturated• solution containing undissolved solute in
equilibrium with the solutionunsaturated• solution containing less than the maximum
amount of solutesupersaturated• solution containing more solute than is
normally allowed
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Henry's Law
Low pressure
Low concentration
Double the pressure equilibrium
Double the concentration
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.
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Cuba diving with trimixtrimix= 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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Henry’s Law
Sg = kHPg
where Sg solubility
kH Henry’s Law constant
Pg partial pressure
of gas
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Solubility of Ionic Compounds and
Temperature
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Parts per Million
#g of solute #mg of solute
ppm = 106 =
#g of solution #kg of solution
#micro-L solute
ppm =
#Lof solution
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Parts per Billion
#g of solute #micro-g of solute ppb = 109 =
#g of solution #kg of solution
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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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Vapor Pressure ofPure Water vs. Sea Water
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Boiling Point Elevation
T = Tfinal - Tinitial
(Tb = bpsolution - bppure solvent)
Tb = kb x m
where kb => boiling point elevation constant
m => molality of all solutes in solution
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Freezing Point Depression
T = Tfinal - Tinitial
(Tf = fppure solvent - fpsolution)
Tf = kf x m
where kf => freezing point depression constant
m => molality of all solutes in solution
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Osmotic Pressure
= cRTi
where => osmotic pressure
c => concentration
R => gas constant
T => absolute temperature
i => number of particles per formula unit
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