Transcript Unit 02 B

Unit 2
IMFA, Solids, Solubility,
Equilibrium, Colligative Properties
By Jojo Hadler and Anna Stobnicki
Solubility Rules
Intermolecular Attractions
Van Der Walls Forces
Types of Attractions
Ion-dipole: attraction of a cat/anion to the respective end
of the permanent dipole
Dipole-dipole: attraction of two dipole molecules (positive
end of one polar molecule is attracted to the negative end
of another polar molecule) Another type of dipole-dipole is
hydrogen bonding. ie. H2O has a H-O covalent bond. The
positive end of this polar molecule is attracted to the
negative end of another water molecule. Also occurs with
H-F and H-N bonds.
Dipole-induced dipole: Polar molecules induce, or create a
dipole moment in a nonpolar molecule
Induced dipole-induced dipole: the electron clouds of two
nonpolar molecules can distort to create a polarization in
neighboring atoms or molecules
Solids
Simple Cubic
1 net atom per unit cell
Cell edge = 2r
Body-Centered Cubic
2 atom per unit cell
Cell diagonal = 4r = (√3)(Length of Edge)
Face-Centered Cubic
4 net atoms per unit cell
Cell diagonal = (√2)(length of edge)
Equilibrium Constants
Equilibrium constant:
[C] c [D] d
K = -------------[A] a [B] b
Expressed as Kc if the equilibrium constant expression
is in moles/liter (M). Expressed as Kp if the equilibrium
constant is in partial pressures
Reaction Quotient:
[C] c [D] d
Q = -------------[A] a [B] b
Le Châtelier’s Principle
Le Châtelier’s Principle:
Effect on K
Effect on K
No Change
No Change
No Change
No Change
Change
Change
Solubilities
Ksp represents the solubility of a molecule into its separate,
equal ion concentrations
ie.
AgCl (s) ↔ Ag+(aq) + Cl- (aq)
Ksp= [Ag+][Cl-]
X2
x=solubility of Ag+ (mol/L)
Reaction Quotient = Q = [products] / [reactants]
Q is used for a chemical reaction that is doesn’t have to be at
equilibrium.
If Q < Ksp then reactants will be converted to products.
If Q = Ksp the system is at equilibrium.
If Q > Ksp some products will be converted to reactants
Colligative Properties
The properties of a solution that depend only on the
number of solute particles per solvent molecules
Raoult’s Law:
Psolvent = Xsolvent Pºsolvent
Boiling Point Elevation:
Adding a solute to a solution increases the temp. at
which it boils
∆Tb =Kbm
Colligative Properties cont…
Freezing Point Depression
Freezing point of a solution is lowered with the
addition of a solute, usually quite small
∆Tf =Kfm
∆Tf = freezing point depression m=molality, Kf=molal
freezing point constant
Other Useful Things
Henry’s Law:
Sg = kHPg
Sg is the gas solubility, Pg is the partial pressure of the
gas solute, and kH is the Henry’s Law constant, a
constant characteristic of the of the solute and
solvent
The End