Download Chapter 13 Notes Types of Solutions Saturated Solution: contains

Chapter 13 Notes
Types of Solutions
Saturated Solution: contains the maximum amount of a solute that will dissolve in a given solvent at a specific temperature.
Unsaturated Solution: contains less solute than it has the capacity to dissolve.
Supersaturated Solution: contains more solute than is present in a saturated solution (very unstable).
Crystallization: the process in which dissolved solute comes out of a solution and forms crystals.
A Molecular View of the Solution Process
*The ease with which a solute particle replaces a solvent molecule depends on the relative strengths of three types of interactions:
1) solvent-solvent interaction
2) solute-solute interaction
3) solvent-solute interaction
3 steps are involved in the solution process: 1) separation of solvent molecules 2) separation of solute molecules 3) solvent and
solute molecules mix
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Solute-solvent attraction > solvent-solvent attraction and solute-solute attraction; exothermic reaction
Solvent-solvent and/or solute-solute attraction > solute-solvent attraction; endothermic reaction
Increase in disorder of the system favors the solubility of a substance, even in an endothermic reaction
Solubility is a measure of how much solute will dissolve in a solvent at a specific temperature (like dissolves like)
Miscible: Liquids that are completely soluble in each other in all proportions. (Alcohols in water)
Salvation: the process in which an ion or a molecule is surrounded by solvent molecules arranged in a specific manner.
(When the solvent is water, this process is called hydration) (Solubility Rules pg. 123)
Concentration Units
Concentration: the amount of solute present in a given amount of solution.
Percent by Mass: (Percent by weight or weight percent) the ratio of the mass of a solute to the mass of the solution, multiplied by
100 percent.
Mole Fraction (X):
Molarity (M):
Molality (m):
Density:
The Effect of Temperature on Solubility
*In most cases, the solubility of a solid substance increases with temperature
Fractional Crystallization: the separation of a mixture of substances into pure components on the basis of their differing solubility
(Works well if the substances involved have greatly differing solubility curves and the contamination/impurity amount is small).
*Generally, gases solubility in water decreases with increasing temperature
The Effect of Pressure on the Solubility of Gases
Henry’s Law: the solubility of a gas in a liquid is proportional to the pressure of the gas over the solution.
Where Sg = solubility of the gas in solution phase, Pg = partial pressure of the gas over the solution,
k = Henry’s law constant
Colligative Properties of Nonelectrolyte Solutions
Colligative Properties: 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).
Nonvolatile: substance does not have measurable vapor pressure.
Volatile: substance that has measurable vapor pressure.
Raoult’s Law: the partial pressure of a solvent over a solution = (vapor pressure of the pure solvent) * (the mole fraction of the
solvent in the solution)
Ideal Solution: Any solution that obeys Raoult’s Law (Benzene in Toluene) (Heat of Solution = 0)
Non-ideal Solutions have 2 cases: 1) Intermolecular forces between A and B molecules are weaker than those forces between A
molecules and B molecules; positive deviation, endothermic reaction. 2) A molecules attract B molecules more strongly than they do
their own kind; negative deviation, exothermic reaction.
Boiling-Point Elevation: (the boiling point of the solution) – (the boiling point of the pure solvent). (Concentration is in molality
because of changing temperature).
Freezing-Point Depression: (the freezing point of the pure solvent) – (the freezing point of the solution). (Concentration is in molality
because of changing temperature).
Osmosis: the selective passage of solvent molecules through a porous membrane from a dilute solution to a more concentrated one.
Semi-permeable membrane: allows the passage of solvent molecules but blocks the passage of solute molecules.
Osmotic Pressure: the pressure required to stop osmosis. (
Isotonic Solution: Two solutions that have equal concentration and the same osmotic pressure.
Hypertonic Solution: The solution of greater concentration in a solution of unequal osmotic pressure.
Hypotonic Solution: The solution of lesser concentration in a solution of unequal osmotic pressure.
Colligative Properties of Electrolyte Solutions
Van’t Hoff factor:
(i=1 for all nonelectrolytes)
*Osmotic pressure = iMRT
Ion pair: one or more cations and one or more anions held together by electrostatic forces
Colloids
Colloid: a dispersion of particles of one substance (the dispersed plane) throughout a dispersing medium made of another
substance.
Aerosol: consists of liquid droplets or solid particles dispersed in a gas (Smoke, Fog)
Emulsion: consists of a liquid droplets dispersed in another liquid (Mayonnaise)
Sol: a suspension of solid particles in a liquid (Milk of magnesia)
Tyndall effect: When a beam of light passes through a colloid, it is scattered by the dispersed phase. This is why the Tyndall effect is
used to help determine a colloid from an ordinary solution.
Hydrophilic: water-loving (proteins)
Hydrophobic: water-fearing (Oil on water)