Ch. 16 Solutions
Ch. 16.1 Properties of Solutions
Solution Formation
• The composition of the solvent and the solute
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determine whether a substance will dissolve.
The speed of dissolving depends on stirring
(agitation), temperature, and surface area of the
dissolving particles.
Stirring or shaking increases rate of solvation by
continually bringing fresh solvent into contact
with the surface of the solute.
• Higher temperature of solvent means
higher avg. kinetic energy of solvent
particles; increased frequency and force
of collisions between solvent particles and
solute surfaces. So faster dissolving.
• Smaller particle sizes dissolve faster, due
to an increased surface area to volume
ratio.
Solubility
• Only a certain maximum amount of salt
will dissolve in a given volume of water at
a given temperature.
• An equilibrium is reached in which the
number of particles leaving the solid and
going into solution equals the number of
particles leaving the solution and
recrystalizing on the solid.
• Saturated Solution—contains the maximum
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amount of solute for a given quantity of solvent
at a constant temp. and pressure.
Solubility—the amount of solute that dissolves in
a given quantity of solvent at a specified temp.
and pressure to produce a saturated solution.
Usually grams of solute per 100 g of
solvent.
• Unsaturated solution—a solution that
contains less solute than a saturated
solution at a given temp. and pressure.
• Some liquids are infinitely soluble in each
other…they are miscible if they dissolve in
all proportions.
• Liquids insoluble in each other are
immicible.
Factors Affecting Solubility
• Temperature—the solubility of most solid
substances increases as temp. increases.
• Supersaturated solution—contains more
solute than it can theoretically hold at a
given temperature. Unstable.
• Gases are more soluble in cold solvents
than in hot . Pressure also affects the
solubility of gases.
Pressure
• Pressure changes strongly affect the
solubility of gases (unlike solids and
liquids). Gas solubility increases as the
partial pressure of the gas above the
solution increases.
• Henry’s Law relates the solubility of a gas
to its partial pressure.
• S1/P1 = S2/P2