1. Solubility and Concentration
Chapter 8
Section 8.2

2. Solubility
Solubility of a substance refers to the maximum amount of that substance that can be dissolved in a given quantity of solvent at a certain temperature.
Solubility values allow us to compare the extent to which different solutes dissolve.

3. Describing Solutions
Saturated Solution: contains as much solute as it can normally hold at that temperature. Can not dissolve any more…
When a solution is saturated, the solvent is “filled” with the solute
Unsaturated Solution: contains less than the saturated amount of solute for that temperature
Supersaturated Solution: contains more solute than a saturated solution can normally hold.

4. Factors Affecting Solubility
Three Factors that affect the solubility of a solute are:
The polarity of the solvent
Temperature
Pressure

5. Polar and Nonpolar Solvents
Recall: A polar molecule has oppositely charged ends (+ and -)
Recall: Non-polar molecules have the same charges on its ends
The phrase “like dissolves like” is used to summarize how well a solute will dissolve in a solvent.
Polar solvents generally dissolve polar solutes very well.
Nonpolar solvents generally dissolve nonpolar solutes very well.
However, polar solvents do not dissolve nonpolar solutes very well and nonpolar solvents do not dissolve polar solutes very well.

6. Temperature
Generally, the solubility of solid solutes in liquid solvents increases with increasing temperature.
The opposite is true of gases.
Gases are less soluble in liquids at higher temps

7. Pressure
Pressure affects only the solubility of gases since liquids and solids are virtually incompressible.
High pressure pushes gas molecules close together and makes them more likely to bond with a liquid solvent. Thus, higher pressure makes gases more soluble.
An increase in pressure (for a gaseous solution) means that more gas has been forced into a smaller volume, so greater chances of successful collisions.
A decrease in pressure means not as much solubility

8. Concentration of Solutions
Concentration of a solution is the amount of solute that is dissolved in a solvent
A solution with a lot of solute dissolved is concentrated
A solution with a little solute dissolved is dilute

9. Concentration: Percent Volume & Mass
Chemists use different measures of concentration depending on the particular situation.
Concentration can be expressed as percent by volume, percent by mass, and molarity.
Percent Volume= Volume of solute x 100 % Volume of solution
Percent by Mass = Mass of solute x 100 % Mass of solution

10. Molarity
Prescription drugs in the correct concentration make you better.
In higher concentration they can kill you.
Chemists need to make solutions that have precise concentrations.
A concentration that expresses the
moles of solute dissolved per liter of solution
Molarity (M) = Moles of solute
Liter of solution