Unit 2 Summery
Solids and Liquids
 Intermolecular Forces (Weakest to Strong)
o London Dispersion – non-polar/non-polar
o Dipole-Dipole – polar/polar
o Hydrogen Bond – ultra polar/ultra polar
 H with N,O,F
o Covalent Bond – non-metal/non-metal
 Cubic Crystal Structures
o Simple Cubic (1 atom)
 V = e3 = 8r3
o Body-Centered Cubic (2 atoms)
o

4r =

V = e3 =(4r/
e
)3
Face-Centered Cubic (4 atoms)

V = e3 = (4r/
)3
o Density = m/v = g/e3
 Phase Changes
o Matter exists as solids, liquids, or gases
o Matter changes between these three phases based on temperature or atmospheric pressure
o Phase Diagrams – show which state matter exist at certain temp and pressure
 Triple Point (T) – all three phases are at equilibrium
 Critical Point (C) – highest temp of pressure where a distinct gas and liquid phase can
exist
 Supercritical Fluid (SCF) – liquid and gas phases are indistinguishable
Solubility
 The amount of substance that can be dissolved in a solvent at a given temperature (g/L)
 Some Simple Solubility Rules
o NO3- is always soluble
o C2H3O2- is always soluble
o See Appendix A-8 for full solubility rules
Equilibrium ( aA + bB  cC + dD )
 Occurs when opposing reactions proceed at equal rates with constant concentrations
 KC = equilibrium constant
o KC = [(C)c(D)d]/[(A)a(B)b]
o No Solids and Liquids included in equation
 Q = Reaction Quotient
o Q = [(C)c(D)d]/[(A)a(B)b]
o When not at equilibrium
o Q < K  Shift Right, Q > K  Shift Left, Q = K  Equilibrium Established
o No solids or liquids included in equation
 KP = KC(RT)-n
 KSP = solubility product constant, this indicates how soluble a solid is in water
o KSP = (C)c(D)d
o Reactants are Solids so they are not included in the equation

LeChâtlier’s Principle – A system in equilibrium, when disturbed, will shift to the extent necessary to
restore equilibrium
o N2 + 3H2
2NH3 + 94K
 Disturbance add N2: reactant is increased so product is increased, shift right
 Disturbance increase temp: tries to lower temp, lower products, shift left
 Disturbance increase pressure: will favor side with fewer moles, fewer moles on product
side, increase products, shift right
 Disturbance add catalyst: reaction goes faster but no change to each side, no shift
 Predicting Formation of precipitates based on Ksp
o Knet = Ksp x Kf
 Kf = formation constant
o Used in reactions with complex ions
o Lower Ksp means it’s less soluble. The combination with a complex ion makes it more soluble (the
Kf value cancels out the Ksp value).
Solutions
 Concentration Units
o Cmolar = nsolute/Vsolution
o Cmolal = nsolute /msolvent (kg)
o Mass Percent = msolute /msolution
o Mole Fraction = nsolute /nsolution
o Volume Fraction = Vsolute /Vsolution
o Parts Per Million (PPM) = msolute (mg) / msolvent (kg) ≈ msolute (mg) / msolution (kg)
 Henry’s Law
o Sg = kHPg
o The solubility of gas increases in direct proportion to the partial pressure above the solution
 Colligative Properties
o Boiling Point Elevation: Tb = iCmolalKb
 i = Van’t Hoff Factor – when dissolved , # of particles the molecule breaks into (Ex.
NaCl = 2)
 Kb = Boiling point elevation constant
 Ions make it harder for water molecules to vaporize, thus requiring more energy to boil
o Freezing Point Depression: Tf = iCmolalKf
 Kf = freezing point depression constant
 Ions make it harder for water molecules to form an orderly crystalline structure
 Raoult’s Law (Vapor Pressure)
o PA = XAPOA
o PA = solution vapor pressure
o XA = mole fraction of solvent (nsolvent/nsolution)
o POA = solvent vapor pressure
o Adding a non-volatile solute to a solution will lower the vapor pressure, thus raising the boiling
point
 Osmosis
o V = nRT
o  = nRT/V = CmolarRT
  = osmotic pressure
 R = 8.314 Pascals (Pa) = 0.08206 atm
o Pressure required to prevent osmosis by a solvent toward a solution with a higher solute
concentration