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TERMS - MIXTURE
2
SOLUTIONa homogeneous
mixture containing particles with the size
of a typical ion or covalent molecule.
(0.1–2.0 nm)
COLLOIDa homogeneous
mixture containing particles with
diameters in the range 2–500 nm
SUSPENSIONare mixtures with even
larger particles, but they are not considered true solutions because they separate upon standing
MiscibilityMiscible – liquids that completely
dissolved together (Think mixable)Immiscible – two liquids that form
layers when mixed together
5
How well something dissolves in a solvent is a solubility
Like dissolves likePolar solutes will dissolve in polar
solventsNon polar solutes will dissolve in non
polar solventsSolubility is affected by temperature.
Increase in temperature will increase the solubility of most of the substances.
Most gases become less soluble in water as the temperature increases.
SOLUBILITY
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A solution is saturated when no additional solute can be dissolved at a particular temperature
A supersaturated solution can form when more than the equilibrium amount of solute is dissolved at an elevated temperature, and then the supersaturated solution is slowly cooled.
An unsaturated solution is formed when more of the solute can dissolve in it at a particular temperature.
SOLUBILITY
SATURATED SOLUTION
no more solute dissolves
UNSATURATED SOLUTION
more solute dissolves
SUPERSATURATED SOLUTION
becomes unstable, crystals form
increasing concentration
SOLUBILITY
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The maximum amount of solute that can dissolve in a specific amount of solvent (usually 100 g.
g of solute 100 g water
SOLUBILITY
LecturePLUS Timberlake 9
Learning Check
At 40C, the solubility of KBr is 80
g/100 g H2O. Indicate if the
following solutions are
(1) saturated or (2) unsaturated
A. ___60 g KBr in 100 g of water at 40C
B. ___200 g KBr in 200 g of water at 40C
C. ___25 KBr in 50 g of water at 40C
Temperature and Solubility Solid solubility and temperature
solubility increases with increasing temperature
solubility decreases with increasing temperature
Temperature and Solubility
Gas solubility and temperature
solubility usually decreases with increasing temperature
12.4
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SOLUBILITY GRAPH OF GASES IN WATER
Pressure has little effect on the solubility of liquids and solids. The solubility of gases is strongly influenced by pressure. Gases dissolve more at high pressure.
COLLIGATIVE PROPERTIES OF SOLUTIONS
Colligative properties are properties that depend only on the number of solute particles in solution and not on the nature of the solute particles.
Vapor Pressure Lowering
Boiling Point Elevation
Freezing Point Depression
Osmotic Pressure
VAPOR PRESSURE LOWERING
Vapor pressure : is the pressure exerted by a vapor in equilibrium with its liquid state.
Liquid molecules at the surface escape into the gas phase
These gas particles create pressure above the liquid in a closed container
BOILING POINT ELEVATION
When a solute is dissolved in a solvent, the boiling point of that solvent is raised.
The temperature difference between a solution’s boiling point and a pure solvent is called the boiling point elevation
Boiling Point Elevation Equation
ΔTb = Kbm
ΔTb = boiling point elevation
Kb = molal boiling point elevation constant (these values change depending on the solvent)
m = molality
FREEZING POINT DEPRESSIONWhen a solute dissolves into
a solvent, the freezing point of that solvent can decline.
The decline is referred to as a freezing point depression.
The freezing point depression is the difference between the solution’s freezing point and the normal freezing point of the solvent.
Freezing-Point Depression of Solutions
DTf = T f – Tf0
T f > Tf0 DTf > 0
T f is the freezing point of the pure solvent
0
T f is the freezing point of the solution
DTf = Kf m
m is the molality of the solution
Kf is the molal freezing-point depression constant (0C/m)
12.6
OSMOTIC PRESSURE OF SOLUTIONSOsmotic pressure is the
minimum pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane
the tendency of a pure solvent to move through a semi-permeable membrane and into a solution containing a solute
ProblemWhat is the boiling point and freezing point of
a 0.058 m aqueous solution of sodium chloride (NaCl)? Kb = 0.512 °C/m
Kf = 1.86 °C/m
What is the solvent?
Solubility CurvesGraphical method of showing solubility of compounds
Used to figure out the amount of solute that will dissolve at any temperature given on the graph, and comparing solubility of compounds.
For example:
At 60 degrees, you can dissolve 100 grams of KNO3. You can only dissolve 55 grams of NH4Cl.
How much of Ce2(SO4)3 can dissolve at 60 degrees?
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