1. Properties of Solutions
Brown, LeMay Ch 12
honors Chemistry
CaCl2 (aq)

2. 13.1: Types of Solutions Example Solvent Solute Air (g in g)
Soda (g in l)
H2 in Pt (g in s)
Alcoholic beverages (l in l)
Sea water (s in l)
Brass (s in s) N2 O2
H2O
CO2 Pt H2
H2O
C2H5OH
H2O
NaCl (one of many salts)
Copper (55% – 90%)
Zinc (10% – 45%)

3. When do solutions form?
Solutions form (the solute and solvent will mix) when:
Energy: solute-solvent interactions are stronger than solute-solute or solvent-solvent interactions.
Disorder: Solutions result in a more disordered state than the separate solute and solvent states, since molecules will be “mixed” that were once “well organized”.
NaCl (s) + H2O (l) → Na+ (aq) + Cl- (aq)
Ion-dipole interactions > H-bonds (H2O···H2O) < Ionic bonds (Na+ Cl-)
The increase in disorder also drives the dissolving process.

4. 13.2: Ways to Express Concentration
Mass Percent
Mole Fraction: commonly used for gases
Molarity: commonly used for solutions
Molality: commonly used for colligative properties
Varies with T
Does not vary with T

5. 13.3: Solubility Vocabulary
Solvation: dissolving; the interactions between solute and solvent
Hydration: solvation with water
Crystallization: “un-dissolving”; process by which solute particles leave the solvent.
Solute + solvent ↔ solution (equilibrium)

6. 13.3: Solubility Vocabulary
Saturated: a solution that is in equilibrium with undissolved solute (appears as solution and crystals)
Solubility: the amount of solute needed to form a saturated solution
Unsaturated: a solution containing less than the saturated amount (appears as solution only)
Supersaturated: a solution containing more than the saturated amount, yet appears unsaturated.

7. 13.4: Factors Affecting Solubility
“Like dissolves like.”
Miscible: liquids that mix (polar or ionic solute with polar solvent, or nonpolar with nonpolar)
Immiscible: liquids that do not mix (polar or ionic solute with nonpolar solvent)
Covalent network solids do not dissolve in polar or nonpolar solvents.

8. 13.4: Factors Affecting Solubility
Pressure: does not significantly affect solubility of liquids and solids
Gases: increased P means increased solubility
Henry’s law: Cg = k Pg
Cg = solubility of gas in solution (M)
k = Henry’s law constant
Pg = partial pressure of gas over solution
English chemist; He began to study medicine at Edinburgh in 1795, taking his doctor's degree in 1807, but ill-health interrupted his practice as a physician, and he devoted his time mainly to chemical research, especially with regard to gases, His Elements of Experimental Chemistry (1799) enjoyed considerable vogue in its day, going through xi editions in 30 years. This book was also translated in Japanese in 1840, as part of the Western studies "Rangaku" movement
William Henry ( )

9. 13.4: Factors Affecting Solubility
Temperature
Most solids: increased T means increased solubility
* Exception: Ce2(SO4)3
Gases: increased T means decreased solubility

10. 13.5: Colligative Properties
Properties that are dependent on the number of solute particles present in solution
Vapor pressure lowering: the greater the concentration of a nonvolatile solute, the lower the vapor pressure of the solvent
Solute takes up surface area
Introduction of solute-solvent IMF
Raoult’s law: PA = XA P°A
PA = vapor pressure of solvent vapor above solution (solute A is nonvolatile)
XA = mole fraction of solute A
P°A= normal vapor pressure of solvent
depression of the freezing-points of liquids by the presence of substances dissolved in them was published in 1878; and continued investigation and experiment with various solvents, such as benzene and acetic acid, in addition to water, led him to believe in a simple relation between the molecular weights of the substances and the freezing-point of the solvent, which he expressed as the loi générale de la congélation, that if one molecule of a substance be dissolved in 100 molecules of any given solvent, the temperature of solidification of the latter will be lowered by 0.63 C. Another relation at which he worked was that the diminution in the vapor pressure of a solvent, caused by dissolving a substance in it, is proportional to the molecular weight of the substance dissolved at least when the solution is dilute.
François-Marie Raoult ( )

11. Ideal solution: described by Raoult’s law
Has low concentration of solute
Solute and solvent have similar types of IMF & molecular sizes

12. Extension of the Liquid Phase
Boiling point elevation:
DTb = i Kb m Kb (H2O) = 0.51 ºC•kg/mol
Freezing point depression:
DTf = i Kf m Kf (H2O) = 1.86 ºC•kg/mol
i = van’t Hoff factor:
Unitless constant associated with the degree of dissociation of a solute in a solvent
Dutch physical and organic chemist and the winner of the inaugural Nobel Prize in chemistry, for his work with solutions. This can generally be summarized by stating that very dilute solutions follow mathematical laws that closely resemble the laws describing the behavior of gases. Predicted that C is in tetrahedron in Had 2 sons and 2 daughters.
Jacobus van’t Hoff ( )

13. Ideal i values i = 1 Substances which do not ionize in solution
Ex: sucrose (sugar)
i = 2 Substances which ionize into 2 ions
Ex: NaCl
i = 3 Substances which ionize into 3 ions
Ex: MgCl2
Ex: Determine the solute “equivalent molality” (factoring in i) for the following solutions:
1-m sucrose
1-m NaCl
1-m CaCl2

14. Osmotic Pressure (P)
Pressure required to prevent osmosis of solute particles
P = iMRT = (n/V)RT
R = L-atm/mol-K
Applied on solution side to stop net movement of solvent from the pure solvent side.
Osmosis: net movement of solvent toward the solution with the highest solute concentration P
Discuss how bottled water is often purified using “reverse osmosis”, i.e. osmotic pressure.
Solvent “wants” to flow
Prevents flow of solute particles

15. 13.6: Colloids Mixtures containing particles intermediate between:
A solution (homogeneous, < 10 Å) and
A suspension (heterogeneous, > 2000 Å)
Tyndall effect: scattering of light seen in a colloid
British, contemporary of Faraday and Darwin, early proponent of evolutionary theory; amazing public speaker; did a free science tour in USA in 1872.
John Tyndall ( )