Solubility, Factors affecting solubility, Solubility Curves, Evaluation of thermal pollution.Solubility of a gas increases with increasing pressure .

1. Solubility Curves
Dr. K. Shahzad Baig
Memorial University of Newfoundland
(MUN)
Canada
Petrucci, et al. 2011. General Chemistry: Principles and Modern Applications. Pearson Canada Inc., Toronto, Ontario.
Tro, N.J. 2010. Principles of Chemistry. : a molecular approach. Pearson Education, Inc.

2. Solubility
• Liquids that mix in all proportions are called miscible.
• Solubility
the mass of solute which will saturate 100 g of solvent at a given temperature
• When there is a dynamic equilibrium between an undissolved solute and a solution,
the solution is saturated.
The quantity of dissolved solute remains constant with time, and the solution is said to
be a saturated solution.
• A solution which contains less solute than can be held at equilibrium is unsaturated.
The solubility of a solid in a liquid generally increases as temperature increases:
the hotter the liquid, the easier it is to dissolve the solid

3. Factors affecting solubility
Temperature
Pressure
Nature of the solvent
Concentration of solutions

4. Solubility Curves
When solubility is plotted against
temperature, a solubility curve is
obtained
The solubility at 58 OC is 20 g per
100 g H2O
The solubility at 82 OC is 40 g per
100g H2O
It will therefore take 40 -20 = 20 g
of the salt to re-saturate the
solution

5. Solubility as a Function of Temperature
• Most ionic compounds have aqueous solubilities that increase significantly with
increasing temperature.
• A few have solubilities that change little with temperature.
• A very few have solubilities that decrease with increasing temperature.
• If solubility increases with temperature, a hot, saturated solution may be cooled
(carefully!) without precipitation of the excess solute.
This creates a supersaturated solution.
• Supersaturated solutions ordinarily are unstable …

6. Effect of Temperature on Solubility of Gases
Thermal pollution:
as river/lake water is
warmed (when used by
industry for cooling),
less oxygen dissolves,
and fish no longer thrive.
O

7. The Solubilities of Gases
At a constant temperature, the solubility (S) of a gas is directly
proportional to the pressure of the gas (Pgas) in equilibrium with the
solution.
C= k Pgas
The value of k depends on the particular gas and the solvent.
The effect of pressure on the solubility of a gas is known as Henry’s law.

8. Henry’s Law
the amount of dissolved gas in a liquid is proportional to its partial pressure above the liquid.
Solubility of a gas increases with increasing pressure
𝑪 = 𝒌 𝑷 𝒈𝒂𝒔
The aqueous solubility of N2 at 0 OC and 1.00 atm is 23.54 mL per liter N2. Suppose we
want to increase the solubility of the N2 (g) to a value of 100.0 mL per liter N2 (g).