Chem II Exam I

intramolecular forces

electrons shared between atoms in a compound (hold molecule together) - strong

intermolecular forces

attractive forces between diff molecules - weak

increasing KE does what for phases?

solid—>liquid—>gas

increasing IMF’s does what to phase changes?

gas—>liquid—>solid

physical prop depends on the balance between ____

the type of IMF

types of IMFs

dispersion, dipole-dipole, h-bonding, dipole/induced dipole, ion/dipole, ion/ion, ion/induced dipole

dispersion forces

instaneous dipoles - random e motion

dispersion forces are present in ____ molecules

all

what leads to stronger dispersion forces

• heavier molecules

• more electrons

• stronger dipole/greater polarization

• larger SA

• higher IMFs

dipole-dipole forces

attractive forces between POLAR molecules - perm dipole

h bonding forces

h directly bonded to N, O, F

• very strong IMF - weak covalent bonds

• all the reasons b4 give higher BP

h bonding are a ____ dipole-dipole

strong

dispersion forces directly correlate _____ to strength of _____

MW, IMF

h-bonding significantly increase ___

boiling point

dipole/induced dipole

occurs between molecules w/perm dipole + another molecule w/t perm dipole

dipole/induced dipole forces are stronger than ____ and weaker than ___

dispersion, dipole-dipole

ion/dipole forces

between an ion + another molecule w/a perm dipole

• very strong interactions (full charged ions w/bigger mag)

ion/ion forces

between 2 ions

• strongest interaction - strength depends on charge (+, 2+, 3+)

ion/induced dipole forces

occurs between an ion + another molecule w/t a perm dipole

ion/induced dipole forces are stronger than ____ and weaker than ____

dipole/induced dipole, ion/dipole

stronger IMF = higher __/__ = ↑ __ = ↑ __

MP/BP, MW, SA

IMFs strongest to weakest

ionic - h-bonding - dipole-dipole - dispersion

MP and BP trends

increases

• down a group, MM ↑, atomic radius ↑

gases take ___ of their container

volume/shape

2 properties of gases

1. particles are far apart w/no reg arrangement

2. particles move ind of one another except during collision

2 properties of liquids

1. particles are close together w/no regular arrangement

2. particles are constantly moving but always in contact

viscosity

resistence of a liquid to flow

properties of viscosity

↑ IMFs = ↑ visc.

↑ temp = ↓ visc.

↑ size = ↑ visc.

surface tension

energy required to increase SA

surface tension between interior molecules

attracted = on all sides

surface tension between surface molecules

uneven/anisotropic ‘pull’ ↓ - surface contracts

• reduce SA as much as it can

capillary action

ability of a liquid to flow against gravity up a narrow tube, dep on interactions between the tube + the liquids

capillary action is a direct consequence of ____

surface tension

cohesion

IMF between identical molecules

adhesion

IMF between diff molecules

smaller tube diameter = more pronounced _____

capillary action

adhesion > cohesion

concave meniscus

adhesion < cohesion

convex meniscus

liquid to gas

vaporization

gas to liquid

condensation

gas to solid

deposition

solid to gas

sublimation

solid to liquid

melting (fusion)

liquid to solid

freezing

vapor pressure

partial pressure of substance above the liquid state

vapor pressure is ___

temp dep

volatile

liquid has a VP (water)

non-volatile

liquid has no VP (glycerol)

stronger IMF = more KE ____

to escape lower VP (at same temp)

↑ T ↑ VP =

higher KE = larger fraction of particles above threshold

vapor pressure ↑/↓

increases with : ↑ T,

decreases with : ↑ IMFs, addition of non-volatile solute

condensation

gas molecules become liquid when they strike the surface + r trapped by IMFs

in a closed container, starting with all liquid and no gas :

• liquid evaporates but cannot disperse

• rate of evaporation remains constant, while rate of condensation ↑

• P ↑, but eventually hits a max

dynamic equilibrium

rate of evaporation and condensation are =

dynamic equilibrium pressure -

the pressure at which this occurs is the VP of the liquid at this temp

in an open container:

• liquid can evaporate completely

• liquid is considered boiling when Vapor Pressure = Exterior Pressure

  • pure vapor bubbles occur throughout the liquid at this point

boiling point

the temp at which the VP = Exterior Pressure

BP can vary with ___

atmospheric pressure (↑ elevation = ↓ P)

BP increases/decreases

decreases: ↑ VP

increases: ↑ IMFs, ↑ atmospheric P, addition of non-volatile solute

normal BP

exterior P = to atmospheric P at sea level (1 atm/760 mmHg)

vaporization is ____

endothermic +

condensation is ____

exothermic -

molar heat of vaporization

heat required to vaporize 1 mol

molar heat of condensation

heat released when 1 mol condenses

enthalpy of vaporization

the amount of heat required to vaporize 1 mol of a liquid to a gas

• decreases with ↑ temp for same substance

a solid melts when …

the KE > IMF holding the particles in their fixed positions

melting is

endothermic

freezing is

exothermic

molar heat of fusion

heat required to melt 1 mol

molar heat of crystallization

heat released when 1 mol crystallizes

enthalpy of sublimation

the amount of heat required to sublimate 1 mol of s—>g

enthalpy is a ____

state function

more energy is required for phase transitions as…

↑ IMF, ↑ PT T, ↑ ΔH_PT

what equation is used - when temp changes within a phase

q=mcΔT (diagonal line)

what equation is used - phase changes

q=nΔH_PT (straight line)

high P, low T =

solid

low P, high T =

gas

Triple Point

point in which all 3 phases in equilibrium

supercritical fluid

at high enough T/P liquid + gas can become indistinguishable

Critical Point

exact T + P beyond which superficial fluid is observed

melting point

temp at which energies of ind particles are sufficient to break free of their fixed positions

crystalline solids

particles are arranged such that there is a repeating long range order in the structure

amorphous solids

there is no long range order to the arrangement of particles within the structure

ionic solids

composed of ions held together by strong electrostatic attraction

• very high MP

• brittle, poor conductors (solid form)

molecular solids

each lattice point is an ind molecule

• held together by IMFs

• soft, low MP, poor conductors

covalent solids

network of atoms held together in 3D by covalent bonds

• very high MP, very hard, brittle, poor conductors

metallic solids

composed of metal atoms

• metallic bonds = electron delocalization

• very good conductors, malleable, ductile, vary in MP typically high

unit cell

most basic repeating (by translation) unit of a crystalline solid

coordination #

number of nearest neighbors (larger value = tightly packed)

1/3rd of all solved crystal structures are ___

monoclinic

Simple Cubic

square open pack

stacking pattern: AAAA

CN: 6

PE: 52%

Body Centered

square open pack

stacking pattern: ABAB

CN: 8

PE: 68%

Face Centered

closed packed

stacking pattern: ABABAB(hexagonal) ABCABC (cubic)

CN: 12

PE: 74%

most solid elements take ____ or ____

FCC/FCH most efficient

not all atoms in a unit cell are ___

equal

empirical formula for unit cells:

corner (1/8)

edge (1/4)

face (1/2)

central (1)

solutions

homogenous mixture of 2/more materials

solvent

subst doing the dissolving, largest fraction (larger concentration)

solute

subst being dissolved, minor fraction (sm concentration)

solutions can be solid (___), gas (___), liquid (___)

alloy, air, aq solution