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140 Chemistry: Matter and Change
Solving Problems: A Chemistry Handbook
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 14
unsaturated solution is one that contains less dissolved solute for
a given temperature and pressure than does a saturated solution. A
supersaturated solution contains more dissolved solute than does a
saturated solution at the same temperature. Supersaturated solutions
are unstable, and the excess solute they contain often precipitates
out of solution if the solution is disturbed.
Various factors affect solubility. For example, most solids are
more soluble at higher temperatures than at lower ones, as shown in
the graph below, which plots solubility versus Celsius temperature
for a number of solutes.
Example Problem 14-1
Determining Solubility
Use the graph above to determine the approximate solubility of
potassium chloride (KCl) at 20°C. How many grams of KCl would
dissolve in 300 g of water at that same temperature? How many
more grams of KCl could be dissolved if the temperature of the
water was raised to 40°C?
Locate the curve representing KCl on the graph. At 20°C, the solubility of KCl is approximately 33 g KCl per 100 g water. Using this
solubility, calculate the amount of KCl that will dissolve in 300 g of
water at 20°C.
0 10 20 30 40 50 60 70 80 90 100
Solubility (g solute/100 g H
2 O)
90
100
80
70
60
50
40
30
20
10
0
Temperature (°C)
Solubilities as a Function of Temperature
NaCl
KClO 3
KCl
CaCl 2
Ce 2 (SO 4 ) 3