Factors Affecting Solubility

Molecular Structure

• “Like dissolves like”• Polar substances dissolve well in polar

solvents• Non-polar substances dissolve well in non-

polar 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 gask – constant of the solutionC – 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 ofa) sugar at 50°Cb) cerium sulfate at 20°Cc) potassium nitrate at 80°C

Temp and Gases

• Solubility of gases decreases with increasing temperature

• What is thermal pollution?