CHEM 119 Exam 3

Lattice Energy

*strength of bond

*What type of bond is stronger than the other?

Strong interactions: higher charge, smaller size

Electronegativity RULES

• 0.0 - 0.4 = Nonpolar Covalent

• 0.5 - 1.9 = Polar Covalent

• Above 1.9 = Ionic

Resonance structures

• multiple valid structures

Formal charges

• sum of FC is charge on molecule

• best = min. formal charges

• charges should be closest to zer

Valence Shell Electron Pair Repulsion Theory

• electrons will repel one another so they are placed as far apart to min. repulsion

• fighting siblings

• bond angle: ideal, less than, greater than

  • ideal = NO lone pairs

  • greater = MORE bonds

  • less = ONE lone pair

2 ELECTRON DOMAIN

• linear, 2 friends and a line

• 180 bond angle

3 ELECTRON DOMAIN

• trigonal planar, tri - 3

• 120

4 ELECTRON DOMAIN

• tetrahedral = 4

• 109.5

5 ELECTRON DOMAIN

• tri(3)gonal bi(2)pyramidal (3+2 =5) , 120 & 90

6 ELECTRON DOMAIN

• octahedral, 90

Molecular geometries

• TRUE geometry

• defined by positions of only the atoms in the molecules, not the nonbonding pairs

ED 3: trigonal planar, molecular

• trigonal planar: 3 bonding , 0 non

• bent: 2 bonding, 1 non

ED 4: tetrahedral, molecular

• tetrahedral: 4 bond, 0 non

• trigonal pyramidal: 3 bond, 1 non

• bent: 2 bond, 2 non

TIP: ED 4 is the same as ED 3 but w one additional one (tetrahedral)

5 ED: trigonal bipyramidal, molecular

• trigonal bipyramidal: 5 bond, 0 non

• seesaw: 4 bond, 1 non

• t-shaped: 3 bond, 2 non

• linear: 2 bond, 3 non

ED 6: octahedral, molecular

• octahedral: 6 bond, 0 non

• square pyramidal: 5 bond, 1 non

• square planar: 4 bond, 2 non

COVALENT Bond length and strength, IMPORTANT STATEM

• the MORE electrons shared, the STRONGER, the SHORTER the bond

miscibility

• property that describes two substances will mix together (dissolve)

Interactions

• NOTE: dipole means polar.

• Ion-Dipole: ion dissolves in polar solvent

• Dipole-Dipole: polar solute dissolves in polar solvent,

• Hydrogen bonding: NO F on this test! strongest!!

• Dispersion forces: weak between NON-polar compounds, larger are more polarizable (MW)

• lewis fo

Phase changes

• vaporization = liquid to gas

• condensation = gas to liquid

• sublimation = solid to gas

• deposition = gas to solid

• triple point

vapor pressure (evaporate)

• weaker intermolecular forces have higher VP: holding hands than hugging (inversely proportional)

• inves

volatile liquids

• liquids that evaporate quickly

• therefore, vapor pressure(evaporation) of ___ is high

altitude

• altitude reduces atmospheric pressure

• therefore, boiling points become lower

energy

• capacity to do work(w) or transfer heat (q)

• Efinal - Einitial = q+w

• if energy is LOST it will be negative to surroundings.

  • this will make something feel hot because it is going onto hands

• if energy is GAINED from surroundings it will be positive

  • vice versa: this will make something feel cold because it is going into system

State functions

• initial and final states of a system

• uppercase variables

• reaction & products, NOT to products

Path functions

• PATH taken to get from initial to final state

• lowercase variables

• work, time, distance

Energy and physical changes

E at solid < E at liquid < E at gas

• gas to solid = looses energy, exothermic

• solid to gas = takes energy, endothermic

Specific Heat Capacity ©

• amount of heat required to raise the temp of one GRAM of a substance by one DEGREE CELSIUS

• molar heat capacity = amt. of heat required to raise temp by MOLES