1. Properties of
Solutions

2. A solution is a homogenous mixture of 2 or more substances.
The solute is(are) the substance(s) present in the smaller amount(s).
The solvent is the substance present in the larger amount.

3. An electrolyte is a substance that, when dissolved in water, results in a solution that can conduct electricity.
A nonelectrolyte is a substance that, when dissolved, results in a solution that does not conduct electricity.
nonelectrolyte
weak electrolyte
strong electrolyte

4. A saturated solution contains the maximum amount of a solute that will dissolve in a given solvent at a specific temperature.
An unsaturated solution contains less solute than the solvent has the capacity to dissolve at a specific temperature.
A supersaturated solution contains more solute than is present in a saturated solution at a specific temperature.
Sodium acetate crystals rapidly form when a seed crystal is
added to a supersaturated solution of sodium acetate.

5. Concentration Units
The concentration of a solution is the amount of solute present in a given quantity of solvent or solution.
Molarity (M)
M =
moles of solute
liters of solution

6. The Energies of
Solution Formation

7. Three types of interactions in the solution process:
solute-solute interaction (separating the solute)
solvent-solvent interaction (overcoming intermolecular forces)
solvent-solute interaction

8. Steps 1 and 2 require energy, since forces must be overcome to expand the solute and solvent.
Step 3 usually releases energy.
Steps 1 and 2 are endothermic and step 3 is often exothermic.
Enthalpy change: enthalpy (heat) of solution (∆Hsoln) is the sum of the ∆H values for the steps:
∆Hsoln = ∆H1 + ∆H2 + ∆H3

9. (a) ΔHsoln has a negative sign (exothermic) if step 3 releases more energy than that required by 1 and 2
(b) ΔHsoln has a positive sign (endothermic) if steps 1 and 2 require more energy than is released in 3

10. What factors affect solubility?
“like dissolves like”
Two substances with similar intermolecular forces are likely to be soluble in each other.
non-polar molecules are soluble in non-polar solvents
CCl4 in C6H6
polar molecules are soluble in polar solvents
C2H5OH in H2O
ionic compounds are more soluble in polar solvents
NaCl in H2O or NH3 (l)

11. Factors Affecting
Solubility
Temperature
Pressure

12. Temperature and Solubility
Solid solubility and temperature – the solubility of most solids increases with temperature.
solubility increases with increasing temperature
solubility decreases with increasing temperature due to entropy (not covered yet)

13. Temperature and Solubility
Gas solubility and temperature
solubility usually decreases with increasing temperature (more energy to escape from solvent)

14. A suspension of tiny particles in some medium is called a colloidal dispersion, or a colloid.
Colloids
The Tyndall effect is used to distinguish between a suspension and a true solution.
Light is scattered by the suspended particles in a colloid.
 Dispersion Medium
 Dispersed Phase
 Type of colloid
 Example
 Gas
 Liquid
 Aerosol
 Fog, mist
 Solid
 Smoke
 Foam
 Whipped cream
 Emulsion
 Mayonnaise, hair cream
 Sol
 Paints, cell fluids
 Pumice, plastic foams
 Gel
 Jelly, cheese
 Solid Sol
 Ruby glass (glass with dispersed metal)