1. Unit 5: Solutions and Solubility
Chemistry 30
Unit 5:
Solutions and Solubility

2. Components of a Solution
A solution is composed of two or more pure substances mixed together, one of which is a solvent and the other a solute.
A cup of instant coffee is the solution, the hot water is the solvent, and the instant coffee is the solute.
A saturated solution is a solution that contains the maximum amount of solute dissolved in a solvent. A supersaturated solution is a solution where conditions have been changed to allow more solute to dissolve than would at room temperature (this is done by heating the solvent or solution).

3. Components of a Solution
Factors that may affect solubility are temperature and pressure:
Temperature: Gases: Temp ⬆, solubility ⬇
Solids and liquids: Temp ⬆, solubility ⬆
Pressure: Gases: Pressure ⬆, solubility ⬆
Solids and liquids: unaffected

4. Components of a Solution
Like dissolves like. That is polar covalent molecules usually dissolve in other polar covalent molecules and non-polar covalent molecules dissolve in non-polar covalent molecules.

5. Components of a Solution
RECALL: Polarity can be determined by subtracting electronegativities. A polar molecule is one where one (or more) atom in the molecule has a stronger pull on the electrons than another atom, so the electrons move closer to the atom with the stronger pull (higher electronegativity). This creates a dipole, where the atom with the stronger pull has a slightly negative charge and the atom with the lower electronegativity (less pull) has a slightly positive charge.

6. Water as a Solvent:
Solutions in which water is the solvent are called aqueous solutions.
Most covalent liquids are only able to dissolve other covalent compounds; water can dissolve both ionic and covalent compounds.
The attraction of water dipoles for ions pulls ions out of a crystalline lattice and into aqueous solution.

7. Aqueous Solutions:
Sometimes when we mix two dissolved salts together, we end up with a precipitate. This is because a new ionic compound is formed that is insoluble in water.
We can use solubility charts or solubility tables to determine if a solid will be formed.

8. Ion
Solubility
Exceptions
NO3–
soluble
none
ClO4–
Cl–
 except Ag+, Hg22+, *Pb2+ I–
except Ag+, Hg22+, *Pb2+
Br-
SO42-
except Ca2+, Ba2+, Sr2+, Hg2+, Pb2+, Ag+
CO32-
insoluble
except Group IA and NH4+
PO43-
OH–
except Group IA, *Ca2+, Ba2+, Sr2+
S2-
except Group IA, IIA and NH4+
Na+ K+
NH4+

9. Ex. If we mix sodium ions with hydroxide ions will a precipitate form?
Solubility
Exceptions
NO3–
soluble
none
ClO4–
Cl–
 except Ag+, Hg22+, *Pb2+ I–
except Ag+, Hg22+, *Pb2+
Br-
SO42-
except Ca2+, Ba2+, Sr2+, Hg2+, Pb2+, Ag+
CO32-
insoluble
except Group IA and NH4+
PO43-
OH–
except Group IA, *Ca2+, Ba2+, Sr2+
S2-
except Group IA, IIA and NH4+
Na+ K+
NH4+
 Ex. If we mix sodium ions with hydroxide ions will a precipitate form?
  Ex. If we dissolved sodium hydroxide in calcium chloride, will a precipitate form?
Ex. Will a mixture of calcium nitrate with sodium carbonate create a precipitate?

10. See Components of Solutions Assign