Chemistry Final Exam

why do intermolecular forces happen

electrostatic interactions

Dipole-dipole forces

exist between polar molecules

symmetrical molecules

nonpolar

nonsymmertical molecules

polar

hydrogen bonding

extreme form of dipole-dipole forces exist between molecules that have H-H, O-H, or F-H bonds

Dispersion forces

exist between molecules in all substances

ion-dipole forces

exist between a charged ion and a polar molecules

strong the IMF on vapor pressure and boiling point

lower vp higher bp

take shape and volume of container

gas

compressible

gas

flow readily

gases and liquids

diffusion occurs rapidly

gas

particles fat apart and not interacting

gas

gas examples

small molecules noble gases

take shape of container but has certain volume

liquids

not compressible

liquids and solids

slow diffusion

liquids and solids

particles close together medium interactions can flow past each other

liquids

have their own shape and volume

solids

do not flow

solids

particles close together strong interactions locked in place

solids

solid examples

metals ionic compounds

physical state of a substance is determined by the strength of the

IMFS and the amount of kinetic energy

higher bp and mp on imf

stronger imf

increase temp increases

kinetic energy

pressure can induce

phase changes

visocity

thickness

higher visocity

lower temp - lower imf

the tension of the surface film of a liquid caused by the attraction of the particles in the surface layer by the bulk of the liquid, which tends to minimize surface area.

surface area def

higher surface tension

stronger imfs

MENISCUS NOTES

the pressure of a vapor in contact with its liquid or solid form.

vapor pressure def

stronger imfs vapor pressure

lower

higher temp on vapor pressure

vapor pressure higher

higher temp on a liquid makes a gas which highers

vapor pressure

volatile

easier evaporated

is IMF stronger with solid liquid or gas

solid

amorphous solids

has no pattern

usually form when a liquid is cooled quickly and solid forms in a more disordered form

particles locked into place before attractive forces can be maximized be orienting everything just right

amorphous solid

crystalline solids

pattern

well-defined melting points crystalline or amorphous

crystalline solids

formed when liquids are cooled slowly to form solids often have well-defined faces or facets

crystalline solid

 the smallest portion of a crystal lattice that shows the three-dimensional pattern of the entire crystal.

unit cell

\
A point at the intersection of two or more grid lines in a point lattice.

lattice point

the symmetrical three-dimensional arrangement of atoms inside a crystal.

crystal lattice

 a set of atoms arranged in a particular way,

motif

one that occurs naturally under certain conditions.

spontaneous

will not take place unless it is “driven” by the continual input of energy from an external source.

nonspontaneous

spontaneous does not tell about the

rate of the reaction

positive delta H

endothermic process

negative delta H

exothermic process

entropy S units

J/K

the measure of a system's thermal energy per unit temperature that is unavailable for doing useful work.

entropy, S

single possibility for all the positions and kinetic energies of all the molecules in a sample; it is a snapshot of positions and speeds at a particular instant p.

microstate

a set of conditions, usually temperature and pressure, that defines the properties of a bulk material

state

more microstates a state has the higher

the entropy

a process that leads to an increase in the # of microstates results in a

positive delta S of system

entropy is larger for solid liquid or gas

gas

solid to liquid to gas entropy of system

increase

number of gas molecules increases entropy of the system

increases

temperature increases entropy of system

increases

volume of system increases entropy of system

increases

an ionic compound dissolves in water entropy of system

increases

entropy of a perfect crystalline substance at absolute zero (0 K) is zero

third law of thermodynamics

at absolute zero all of the molecular motions

stop

standard molar entropy increases with

increases molar mass, increased # of atoms in the formula

in any spontaneous process there is always an increase in the entropy of the universe

second law of thermodynamics

positive delta universe

spontaneous in forward direction

negative delta nuiverse

nonspontaneous in forward

reverse direction is spontaneous

delta s of universe equal to zero

no tendency to occur (at equilibrium)

exothermic reaction increase -- of surrounding

entropy

endothermic processes release heat into system decrease in --- of surroundings

decrease

delta g negative

spontaneous in forward direction

delta g positive

nonspon in forward

reverse direction is spontaneous

delta g zero

has no tendency to occur at equilibrium

gibbs free energy for spontaneous process

the free energy is the maximum amount of energy released by the system that can do useful work

energy available to drive nonspontaneous processes

the products are downhill from the reactants

gibbs free energy for nonspontaneous process

the free energy is the minimum amount of work that must be done to force the process to occur

four factors that affect rate

physical state of reactants

reactants concentrations

reaction temp

presence of a catalyst

increasing the concentrations of the reactants increases the

rate and frequency of collisions

heterogeneous reaction

reactants are of different phases

increases the rate of a reaction without being used up

catalyst

the equation that shows how the reaction rate depends on reactant concentration is

rate law

overall order

is the sum of all the exponents

double concentration of a reactant while holding the other constant and the rate doubles then your order with respect to the reactant is

1

if you double the concentration of a reactant while holding the other reactants constant the rate quadruples then your order is

2

if you double the concentration of a reactant while holding the concentration of the other reactants constant and the rate does not change then your order is

0

rates of most reactions increase as

temperature increases

the minimum energy required to initiate a particular chemial reaction

the activation energy Ea

the lower the E

the faster the rate

the molecule that corresponds to the top of the energy barrier on a reaction coordinate

transition state

determined by the number of molecules that participate as reactants in that step

molecularity of a step

single molecule is the reactant

unimolecular

step involves collision of two molecules

bimolecular

the step involves the collision of three molecules

termolecular

elementary reactions occur in a

single step

rate law for an elementary reaction is determined by the

molecularity

when you add up the elementary steps in a proposed mechanism they must add up to

the given chemical equation for the overall process

a species that is formed in one elementary step and consumed in the next

intermediate

slowest step is called the

rate-determining step

slowest step in a multistep mechanism reaction determines

the overall rate