CHM 142 Exam 1 Flashcards
weakest of the intermolecular forces, present in all molecules
london-dispersion forces
the attraction of the - and + charges of ions
dipole-dipole interactions
when H is bonded to O N or F
hydrogen bonding
attraction between an ion and a polar molecule, strongest of the forces
ion-dipole interaction
when a dissolved solutes particles re-attatch in a solution to form a solid
crystallization
a solution that has the amount of solute added that is measured by solubility
any more solute added will not dissolve
saturated
the amount of solute needed to saturate a solution
max amt of solute that can be added
solubility
the—the attraction between a solute and solvent the — the solubility of the solute in that solvent
stronger, greater
does hydrogen bonding increase or decrease solubility?
Increases solubility
liquids that mix in all proportions no matter the amount
miscible
liquids that do not and can not mix
immiscible
is the solublity of liquids and solids affected by pressure?
no, but gases are
the solubility of a gas is — to its partial pressure
proportional
will increase if P increases, will decrease if P decreases
solublity of a gas in a solvent=
K Pg
K= constant
P= partial pressure of gas
how does temperature affect the solubility of gases?
as temperature increases the solublity of the gas decreases
gas escapes through bubbles when soln boils
mass percentage =
mass of solute/ total mass of soln * 100
ppm=
mass of solute/total mass of soln * 10^6
ppb=
mass of solute/total mass of soln *10^9
molality
moles of solute/ mass (Kg) of solvent
molarity
moles of solute/ volume (L) of soln
what do you need to convert to molarity if you’re using ppms or ppb
density
is molality affected by increasing temp?
no, increasing temp does not change moles
it does affect molarity (V)
properties that depend on the quantity (aka concentration) of molecules and not the identity of the molecule
vapor pressure, boiling point, freezing point, osmotic pressure
Colligative properties
the pressre exerted by a gas over a liquid while in equilibrium
vapor pressure
how do you calculate partial pressure?
total pressure * the mole fraction of the the moleucle
when a solute is added to a pure solvent what happens to the vapor pressure?
the vapor pressure is lowered
less molecules can escape as gas so VP is lower
vapor pressure of a soln=
pressure of solvent * mole fraction of solvent
moles of component/ total moles
mole fraction
is the boiling point of a solution lower or higher than that of a pure solvent?
it is (typically) higher than that of a pure solvent because the vapor pressure is lower so it takes a higher temp to boil the solution
change in BP of a soln=
iKbm or boiling point of soln. - boiling point of the solvent
the number of ions a molecule dissociates into when placed in a solvent
van hoff factor
it is 1 for nonelectrolytes
is the freezing point of a solution higher or lower than the FP of a pure solvent?
it is lower than the pure solvent
think about icing roads and what the ice does to the water on the road
Osmotic Pressure
equation
IMRT
i(n/v)RT
Osmotic Pressure
defenition
the pressure needed to stop osmosis
the movement of solvent molecules from a solution of low concentration (high solvent) to high concentration (low solvent)
osmosis
what happens if two solutions are isotonic?
aka osmotic pressure is equal
No osmosis occurs
what does it mean if a solution is hypertonic?
high osmotic pressure
what does it mean if a solution is hypotonic?
low osmotic pressure
dispersion of a soltue where the particles do not evenly/completely dissolve
intermediate kind of dispersion
colloids
what allows colloids to be able to scatter light while solutions cannot?
the tyndall effect (and their larger molecules)
all of the reactants exist in the same state of matter
Homogenous reactions
the reactants exist in different states of matter
heterogenous reactions
do heterogenous or homogenous reactions proceed at faster rates?
homogenous reactions
how does concentration affect reaction rates?
the higher the concentration of reactants the quicker the reaction proceeds
more opportunities for mlecules to collide
-change in concentration/ change in time
reactants
rate of dissappearnace
rate of appearance
product
change in concentration/ change in time
the rate of of a particlar instant/ point in time of a reaction
instantanous rate
t=0
initial rate
how do you calculate the instant rate when the products and reactants dont have a 1:1 ratio?
-1/a({A}/change in time)=1/b({B}/change in time)
General Rate law
rate =k{A}^x*{B}^y
the exponents x and y (or m and n) in the rate law equation that determine how the rate is affected by the reactants
reaction order
when the rate depends on a single reactant to the 1st power
first order reaction
rate=k{A}
rate law for first order reactions
ln{A}=-kt+ln{A}0
Integrated rate law for first order reactions
when the rate depends on one reactant to the second power or two reactants to the first order
second order reactions
=K{A}^2
rate law for second order reactions
integrated rate law for second order reactions
1/{A}=kt+1/{A}0
when the rate of disappearance of a reactant is independent of concentration
Zeroth order reactions
rate =k
rate law for zeroth order reactions
=kt+{A}0
integrated rate law for zeroth reactions
half-life for first order reactions
-ln(1/2)/k
half-life for second order reactions
1/k{A}0
rate laws relate — and —
rate and concentration
integrated rate laws relate— and —
time and concentration
molecules in a reaction must be aligned in the correct way to create a reaction/ form and break bonds
orientation factor
the minimum energy required to complete a chemical reaction
activation energy
the arrangment of molecules at the ‘peak’ of the Ea
not an intermediate
activation complex/transition state
the — the value of activation energy the — the rate constant
lower, greater
or greater and lower
fraction of molecules with the energy to reach the activation energy
f= e^(-Ea/RT)
Arrhenius Equation
k=Ae^(-Ea/RT)
equation for determining the activation energy when you have 1 rate constant
Ln(k)=-Ea/RT+ ln(A)
eqaution for determing the activation energy when you have 2 rate constants
ln(k1/k2)=-Ea/R(1/T2-1/T1)
reactions that occur in a single step/event
elementary reactions
A—products
one step, one molecule
unimolecular
A+B—products
or A+A—products
bimolecular
true or false, the steps of a chemical reaction always add up/cancel out to a new reaction equation?
false, they will always result in the original equation
not an initial reactant or intial product in the reaction, it is only seen in the reaction steps
and is used up in the steps
Intermediate
for a mechansism with a slow first step
rate law=
the rate of the slow first step
a substance that is not affected/ used in a reaction that also increases the reaction rate
lowers activation E or changes orientation of molecules
catalyst
when catalysts are in the same phase as the reactants
homogenous catalysis
when the catalysts are in different phases than the reactants
heterogenous catalysis
when molecules attatch to the bind to a surface
they do not permeate the inside
Adsorbtion
biological molecules that use the Lock-in Key model and are very specific about what they choose to react with
Enzymes
when reactants and product concentration is no longer changing but forward and reverse reactions are continuing to happen
equilibrium state
Kc/Keq=
The concentration of products/ concentration of reactants to their coefficients
How to calculate Kc/Keq for gases
Kp= Kc(RT)^change in moles
you can also use the pressures like you would use concentrations
if Kc/Kp»1 what does this indicate?
that the reaction favors the products
lies to the right, numerator is larger
If Kc/Kp«1 what does this indicate?
that the reaction favors the reactants
lies to the left, large denominator
