solubility: the amount of solute needed to form a
saturated solution in a given quantity of
solvent under given conditions of T and P
saturated: soln is in eq. w/undissolved solute
i.e., there is solid at the bottom
unsaturated: more solute could dissolve
i.e., soln is clear (MIGHT be colorless)
supersaturated: the amount of dissolved solute
exceeds the solubility
-- soln has a clear, water-like appearance, but
is VERY unstable
-- addition of a seed crystal causes excess
solute to crystallize, leaving a sat. soln.
(w/visible solid)
A supersaturated solution crystallizing
upon the addition of a seed crystal. The
resulting solution is then saturated.
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Sol. Curve for a Typical Substance
Dissolved in a Liquid
solid in liquid
Solubility
(g/100 g H2O)
supersaturated
saturation limit
(i.e., solubility)
gas in liquid
unsaturated
T (oC)
-- for solids, as T
, sol. ___
-- for gases, as T
, sol. ___
Factors Affecting Solubility
Solute-Solvent Interactions
-- As IMFs between solute and solvent increase,
increases
solubility _________.
miscible: describes pairs of liquids that mix in
all proportions (v. immiscible)
d+
d+
d+
d–
d–
Methanol, which is used to fuel race cars,
is miscible with water due to its highly
polar nature.
Low molar mass alcohols are completely miscible in
water, due to H-bonding of hydroxyl group (–OH);
as molar mass increases, the polarity of the alcohol
molecule... decreases (it behaves more like a pure
hydrocarbon) and miscibility decreases.
e.g., CH3OH vs. CH3CH2CH2CH2OH
-- Substances with similar IMFs tend
to be soluble in one another;
“like dissolves like.” (pol/pol and np/np)
-- Some network solids aren’t
soluble in either polar or nonpolar solvents because of
strong forces within the solid.
Pressure Effects
-- Pressure has no effect on the solubility of solids in
liquids, but as P increases, gas solubility ___.
-- Henry’s law:
Sg = k Pg
Sg = solubility of the gas in
the solution (M)
k = Henry’s law constant; it
depends on solute, solvent,
and temp. (M/pres. unit)
Pg = partial pressure of the
gas over the solution
(pres. unit)
William Henry
(1775 – 1836)
A bottled soft drink at 25oC has CO2 gas at a pressure
of 5.0 atm over the liquid. If the partial pressure of CO2
in the atmosphere is 4.0 x 10–4 atm and the Henry’s
law constant for CO2 over water at 25oC is
3.1 x 10–2 M/atm, calculate the solubility of the CO2
both before and after the bottle is opened.
AFTER
BEFORE
Sg = k Pg
Sg = 3.1 x 10–2 M/atm (5.0 atm)
= 0.16 M
(fresh)
Sg = 3.1 x 10–2 M/atm (4.0 x 10–4 atm)
= 1.2 x 10–5 M
(flat)
Ways of Expressing Concentration
qualitative: concentrated v. dilute
quantitative:
mass of component
mass % 
mass of solution
ppm =
ppb =
ppt =
1 ppm  1 mg/L of soln
x 100
x 106
x 109
x 1012
moles of component
mole fraction, X 
total moles
moles of solute
molarity, M 
liters of soln
moles of solute
molality, m 
kg of solvent
Unlike molarity, molality doesn’t
change with temp. because...
mass remains constant w/
changing T. (V changes w/T.)
To go between molarity and
molality, you need…the soln’s density.
A 5.5-g sample of well water contains 0.75 mg of
lead ions. In ppm, find the concentration of lead ions.
mass of comp.
ppm 
x 10 6
mass of soln.
0.75 x 106 g
ppm 
x 106
5.5 g
= 0.14 ppm
140 ppb (!!!)
The federal limit for lead in
drinking water is 15 ppb.
100 g
bleach
If a commercial bleach is 4.35% sodium hypochlorite
by mass, calculate the bleach’s mole fraction and
molality of the sodium hypochlorite.
 1mol 
 = 0.05839 mol NaClO
4.35 g NaClO 
 74.5 g 
 1 mol 
 = 5.3139 mol H2O
95.65 g H2O 
 18.0 g 
0.05839
X
= 0.0109
0.05839  5.3139
0.05839 mol
m
= 0.610 m
0.09565 kg