Factors Affecting Solubility
Molecular Structure
• “Like dissolves like”
• Polar substances dissolve well in polar
solvents
• Non-polar substances dissolve well in nonpolar solvents
• Has to do with the heats absorbed or released
in the dissolving process
H1 H2 H3 Hsoln Outcome
------------------------------------------------------------Polar Solute,
Polar Solvent
Polar Solute,
Non-Polar solv
Non-polar solute,
Non-Polar solv
Non-polar solute,
Polar Solvent
Pressure
• Has little or no effect on the solubilities of
liquids or solids
• Has a great effect on the solubility of gases
• Higher the pressure, the greater the solubility
of a gas
Henry’s Law
• The amount of gas dissolved in a solution is directly
proportional to the pressure of the gas above the
solution
P = kC
P- partial pressure of the gas
k – constant of the solution
C – concentration of the solution
Example
• A soft drink is bottled so that a bottle at 25°C
contains carbon dioxide gas at a pressure of
5.0atm over the liquid. The Henry’s law
constant for carbon dioxide in solution is 32 L
atm/mol. Calculate the concentration of
carbon dioxide in the soda.
Temperature
• For most solids and liquids, solubility
increases with increasing temperature
• For some though, solubility decreases as
temp increases
• There is no way to really predict how
solubility of liquids and solids will change with
temp.
• Experimental results are the only thing
reliable
Example
• From solubility graph on page 525, tell
solubility of
a) sugar at 50°C
b) cerium sulfate at 20°C
c) potassium nitrate at 80°C
Temp and Gases
• Solubility of gases decreases with increasing
temperature
• What is thermal pollution?