Chemistry Test One

Dispersion Forces
Random electron motion produces an unbalanced charge distribution producing a temporary dipole
Halogens
Fluorine
chlorine
bromine
iodine
dispersion forces occur for
all particles
the relative strength of dispersion forces depend on
the polarizability of the particle
polarizability depends on
the number of electrons and the shape of the particles
the total number of energy levels produced equals the
total number of orbitals used
the hydrogen bond is a special case of
dipole dipole interaction
DNA is an example of ____ bonding
hydrogen
a solution is a ______ mixture
homogeneous
the solubility is the
maximum amount of solute that will dissolve in a fixed quantity of solvent
miscible:
soluble in each other in all portions
immiscible:
not soluble in any portions
saturated:
all it can hold
unsaturated:
can hold more
supersaturated:
more than it can hold
molarity (M) equation
mol of solute / L of solution
molality (m) equation
mol of solute / mass (kg) of solvent
parts by mass equation
mass of solute / mass of solution
parts by volume equation
volume of solute / volume of solution
mole fraction equation
mol of solute / (mol of solute + mol of solvent)
substances with similar types of intermolecular forces ____ in each other
dissolve
solute particles separate from each other
endothermic
solvent particles separate from each other
endothermic
solute and solvent particles mix
exothermic
solvation of ions by water is always
exothermic
the idea of energy was first developed by
clausius
solubility of gases usually decrease with
temperature
henry’s law
solubility of gases in a liquid is proportional to the pressure of the gas over the liquid
Boiling point elevation
DTb =
Kbm
Freezing point depression
DTf =
Kfm
Osmotic Pressure Equation
pie = M R T
where M is the molarity,
R is the ideal gas law constant and
T is the Kelvin temperature
symbol of osmotic pressure is
pie
The van’t Hoft factor, i, tells us
hat the “effective”
number of ions are in the solution.
i =
measured value for electrolyte solution/
expected value for nonelectrolyte solution
Four factors can be controlled during the reaction
1. Concentration – molecules must collide to react;
2. Physical state – molecules must mix to collide;
3. Temperature – molecules must collide with enough energy to react;
4. The use of a catalyst.
reaction rate –
changes in the concentrations of reactants or products per unit time
reactant concentrations ______ while product concentrations _____
decrease; increase
Rate =
k [A]^m [B]^n
k = rate constant
m = order of reaction in A
n = order of reaction in B
m+n = overall order of reaction
Collision Theory
Chemical Reactions occur during collisions
The Collision must be effective:
1. Have enough energy to produce the reaction
2. Have the correct orientation to produce the reaction
Transition state theory (TST) explains
the reaction rates of elementary chemical reactions.
The theory assumes a special type of chemical equilibrium (quasi-equilibrium) between reactants and
activated transition state complexes
A complex reaction can proceed by a series of _____ ______
elementary reactions
The rate of reaction is often determined by one slow step
(rate-determining or rate- limiting step).
Homogeneous Catalysts
They are in the same phase as the reactants (usually liquid)
Homogeneous Catalysts are Often
acids, bases, transition metal complexes
Heterogeneous Catalysts
Catalyst is in a different phase from the reactants (usually solid)
____ are considered Heterogeneous Catalysts
Enzymes
phase
each physical state
potential energy in the form of intermolecular forces tends to
draw the molecules together
kinetic energy associated with the random motion of molecules tends to
disperse the molecules
intramolecular forces exists
within each molecule
intermolecular forces exist
between each molecule
gas compressibility is
high
liquid compressibility is
very low
solid compressibility is
almost none
gas ability to flow
high
liquid ability to flow
moderate
solid ability to flow
almost none
gas to liquid
condensation
liquid to gas
vaporization
liquid to solid
freezing
solid to liquid
fusion or melting
gas to solid
deposition
solid to gas
sublimation
exothermic changes
condensing, freezing and depositing
endothermic changes
melting, vaporizing and subliming
heating cooling curve shows
the change in temperature of a sample when heat is absorbed or released at a constant rate
symbol for heat
q
within a phase, heat flow
is accompanied by a change in temperature
during a phase change heat flow
occurs at a constant temperature
liquid gas open system
nonequilibrium process
liquid gas closed system
equilibrium process
dynamic equilibrium
the rate of condensation equals the rate of vaporization, form this point forwards the pressure is constant
temperature has a major effect on water vapor because
it changes the fraction of molecules moving fast enough to escape the liquid and, by the same token, the fraction moving slow enough to be recaptured
the _____ the temperature, the ____ the vapor pressure
higher; higher
the ______ the intermolecular forces, the _____ the vapor pressure
weaker; higher
boiling point is
the temperature at which the vapor pressure equals the external pressure
the boiling point depends on the
applied pressure
melting point is
the temperature at which the melting rate equals the freezing rate
water expands upon
freezing
bonding forces are relatively strong because
larger charges are closer together
intermolecular forces are relatively weak because
smaller charges are farther apart
what force takes place when an ion dissolves in water
ion dipole force
ion dipole force
when an ion and a nearby polar molecule attract
dipole-dipole force
the positive pole of one molecule attracts the negative pole of another
Hydrogen bond
when an H molecule bonds with an O, N or F molecule
boiling points rise with
increased molar mass
polarizability
how easily the electron cloud of an atom can be distorted
smaller particles are _____ polarizable than larger ones
less
polarizability increases
down a group because atomic size increases
(larger/smaller) electron clouds are easier to distort
larger
polarizability decreases
across a period
Dispersion force
intermolecular force responsible for the condensed states of nonpolar substances
dispersion forces are present in
all atoms, ions and molecules because they are caused by the motion of electrons in an atom
an interior molecule is attracted by others
on all sides
a surface molecule is attracted by
other below and to the sides, so it experiences a net attraction downward
forces in CH3CH2OCH2CH2
dipole-dipole and dispersion
forces in CH3CH2OH
H bonding
Forces in CH3CH2CH2CH2OH
H bonding and dispersion
Forces in H2O
H bonding
Forces in Hg
metallic bonding
viscosity
the resistance of fluid to flow
viscosity decreases with
heat
surface tension is
a measure of the energy required to increase a liquid’s surface area
capillary
the rising of a liquid through a narrow space
viscosity depends on
molecular shape
the great solvent power of water results from its
polarity and h bonding ability
crystalline solids have
well defined shapes because of their particles occur in an orderly arrangement
amorphous solids have
poorly defined shapes because their particles lack an orderly arrangement
examples of amorphous solids
rubber and glass
the centers of 8 identical particles define the corners of a cube
simple cubic unit cell
the simple cubic unit cell has a coordination number of
6
coordination number
number of nearest neighbors of a particle
identical particles lie at each corner and at the center of the cube
body centered cubic unit cell
the body centered cubic unit cell has a coordination number of
8
identical particles lie at each corner and in the center of each face but not in the center of each cube
face centered cubic unit cell
the face centered cubic unit cell has a coordination number of
12
packing efficiency
percentage of the total volume occupied by the spheres themselves
hexagonal unit cell has ______ _____ packing
Hexagonal closet
face centered unit cells has ______ _____ packing
cubic closest
atomic solids
individual atoms held together only by dispersion forces
only substances that form atomic solids
noble gases
inter-particle forces in atomic solids
Dispersion
inter-particle forces in molecular solids
disoersion, dipole dipole and h bonding
inter-particle forces in ionic solids
ion ion attraction
inter-particle forces in metallic solids
metallic bonds
inter-particle forces in network covalent solids
covalent bonds
examples of network covalent solids
graphite and diamond
electron sea model proposes
that all metal atoms in a sample pool their valence electrons to form an electron sea that is delocalized throughout the piece
the regularity and mobility of the valence electrons in the electron sea model of metallic bonding account for three major physical properties:
phase change, mechanical properties and conductivity
the valence and conduction bands of a conductor have _______ energy gap so
no; electrons flow when a tiny electrical potential difference is applied
the valence and conduction bands of a semiconductor have _______ energy gap so
small; thermally excited electrons can cross the gap, allowing a small current to flow
the valence and conduction bands of a insulator have _______ energy gap so
large; no current is observed even when the substance is heated
mixtures
two or more substances mixed together physically, not combined chemically
mixture has two defining characteristics:
1) its composition can be variable
2) it retains some properties of its components
a ____ dissolves in a ____ to form a solution
solute; solvent
ion induced dipole forces arise when
an ion’s charge distorts the electron cloud of a nearby nonpolar molecule
dipole induced forces arise when
a polar molecule distorts the electron cloud of a nearby nonpolar molecule
intermolecular forces listed in decreasing strength
ion-dipole
H bond
dipole-dipole
ion-induced dipole
dipole-induced dipole
dispersion
solubility in water is high for
smaller alcohols
solubility in water is low for
larger alcohols
solubility in hexane is low for
the smallest alcohol
solubility in hexane is high for
larger alcohols
gas gas solutions
all gases are miscible with each other
gas solid solutions
when a gas dissolves in a solid, it occupies the spaces between the closely packed particles
solid solid solutions
solids diffuse so little that their mixtures are usually heterogeneous
alloys
mixtures of substances that have a metallic character and are solid solid solutions
solvation
the process of surrounding a solute particle with solvent particles
hydration
solvation in water
change density
ratio of a ion’s charge to its volume
heats of hydrations exhibit trends based on
the ion’s charge density
entropy
freedom of motion of particles
a _____ usually has higher entropy than the ______ solute or solvent
solution; pure
most solids are more soluble at
higher temperatures
the solubility of any gas in water decreases with
rising temperature
____ has little effect on liquids and solids because
pressure; the are almost incompressible
Henry’s Law
the solubility of a gas is directly proportional to the partial pressure of the gas above the solution
symbol for Henry’s Law constant
KH
volume percent =
(volume of solute / volume of solution ) x100
mole percent =
mole fraction x 100
density =
mass/ volume
colligative properties of solutions
vapor pressure lowering, boiling point elevation, freezing point depression and osmotic pressure
electrolyte
conducts electricity
non electrolyte
doesnt conduct electricity
strong electrolyte
soluble salts, strong acids, strong bases
dissociate completely into ions
weak electrolytes
weak acids and bases
dissociate very little into ions
Raoult’s Law
vapor pressure of solvent above a solution equals the mole fraction of solvent times the vapor pressure of the pure solvent
semipermeable membrane
ones that allows solvent but not solute to pass through
osmosis
net flow of solvent into the more concentrated solution
the net flow of water into a solution increases its ______ and decreases its _______
volume; concentration
osmotic pressure
pressure that must be applied to prevent net movement of water from solvent to solution
chemical kinetics
study of how fast change occurs
reaction rates
change in the concentrations of reactants (or products) as a function of time
reaction rate is proportional to
concentration of reactants
the greater the surface area
the faster the reaction occurs
concentration affects rate by
influencing the frequency of collisions between molecules
physical state affects rate by
determining how well reactants mix
temperature affects rate by
influencing the frequency and the energy of the collisions
rate of motion (speed) =
change in position / change in time
rate =
-D[A] / Dt
the average rate is
the slope of the line joining tow points on the curve
instantaneous rate
rate at a particular instant during the reaction
initial rate
instantaneous rate at the moment the reactants are mixed (at t=0)
the rate law expresses the rate as
a function of concentrations and temperature
rate law equation
Rate = k[A]^m[B]^n
symbol for rate constant
k
three lab methods for determining the initial rate
change in color
change in pressure
change in conductivity
the reaction is first order overall if
the rate is directly proportional to [A]
the reaction is second order overall if
the rate is directly proportional to the square of [A]
the reaction is the zero order overall if
the rate is not dependent on [A] at all, the rate doesn’t change when [A] changes
half life
times is takes a given reactant concentration to reach half of its initial value
the half life of a second order reaction is
inversely proportional to the initial reactant concentration
the half life of a zero order reaction is
directly proportional to the initial reactant concentration
collision theory
particles (atoms, molecules or ions) must collide to react
activation energy
energy threshold that the colliding molecules must exceed in order to react
if particles move faster they collide _____
more often
reaction mechanism
sequence of single reaction steps that sum to the overall equation
rate determining step limits
how fast the overall reaction proceeds
reaction intermediate
substance formed and used up during the reaction