Exam 2 Flashcards
system
anything we define it as
open system
energy & mass can enter & exit
closed system
only energy can enter & exit; matter cannot
isolated system
neither energy nor mass can enter or exit
Surroundings
everything outside a defined system
state of a system
measurement of relevant properties (state functions)
state functions depend on…
final & initial states, not how they are achieved
9 state functions
mass
pressure
temperature
volume
particle number
entropy
enthalpy
Gibbs free energy
internal energy
heat
transfer of thermal energy between 2 bodies of different temp
q
heat
m
mass
P
pressure
T
temperature
B/V
volume
E
energy
U/I
internal energy
G
Gibbs free energy
H
enthalpy
S
entropy
entropy
measure of disorder
relation between entropy & moleculer weight
entropy rises & falls with molecular weight
EQUATION
S = _____ W
W =
Used for simple systems
S = K ln W
W = Xn
Xn = (cells in a volume)molecules
K = ___ + C
273
spontaneous or non-spontaneous:
(+/-) change in entropy
(+) = spontaneous
(-) = nonspontaneous
spontaneous or non-spontaneous:
(+/-) change in Gibbs
(+) = nonspontaneous when forward
(-) = spontaneous when forward
what is prime ‘ used for
living systems
K = Boltzman constant =
1.38 x 10-23
R = gas constant =
8.314 J/mol K
W =
number of different arrangements
Xn =
(cells in a volume)molecules
Avogadro’s number
6.022 x 1023
standard conditions
1 atm
1.00 M
pH 7
25 C
pure solids & liquids
most stable allotropic form of elements at std conditions
1st law of TD
energy cannot be created or destroyed, only transduced
2nd law of TD
entropy of the universe is always increasing
3rd law of TD
the entropy of a perfect crystalline substance is zero at 0 K
spontaneous process
occurs under a specific set of conditions
S increases with… (5)
molar mass
molecular complexity
temperature
volume
when a rxn produces more gas molecules than it consumes
exergonic
products at lower energy state than reactants
G is (-)
endergonic
products at higher energy state than reactants
G is (+)
When H is (-) and S is (+), G is ___ and will be _______
negative
spontaneous
When H is (+) and S is (-), G is ___ and will be __________
positive
non-spontaneous
2 necessary components of an effective collision
- enough Ea
- correct orientation
there are more effective collisions with…
increased temp, stirring, increased concentration
reaction rate is proportional to…
effective collisions per second
activation energy
minimum energy required to initiate reaction
effective collisions result in…
an activated complex during the transition state
average rate
change in concentration over a specific period of time
instantaneous rate
rate of the reaction at one point in time
instantaneous rate =
k[A]
k = rate constant
RATE EXPRESSION
rate law definition
equation that relates the rate of reaction to the concentration of reactants
rate law (in general)
rate = k[A]x[B]y
x in rate law =
order of A
y in rate law =
order of B
To find X & Y in rate law
- in the information given, find 2 different concentrations of A in which the concentration of B is constant
- divide one by the other
- for these same sets of data, divide one rate of A by the other rate of A
- rate quotient = (concentration quotient)x or y
- do the same for B, using y
find the exponent in TI-83
log(product) / log(base) = exponent
how to do inverse of natural log
ln(x) = y
→
x = ey
A in Arrhenius equation =
collision frequency/frequency factor
how to find overall reaction order
sum of the exponents on reactants in rate law
3 important things about rate law
- exponents must be determined from experimental data
- rate depends on concentration of reactants
- reaction order is determined by reactant concentrations, never product concentrations
intermediates
species that appear in reaction mechanism, but not products or reactants
elementary reaction
single collision of reactant molecules
molecularity
number of reactant molecules involved in a collision
unimolecular, bimolecular, termolecular
refers to # of reactant molecules in an elementary reaction
rate-determining step
slowest step in reaction
2 requirements for reaction mechanisms
- sum of elementary reactions must be the balanced overall equation
- rate-determining step must have the same rate law as that determined by experimental data for the overall reaction
step with the highest Ea
rate-determining step
catalyst
substance that increases rate of reaction by providing an alternate pathway for the reaction with a lower Ea
catalysts reduce…
entropy
importance of colliding at correct orientation
heterogeneous catalyst
reactants & catalysts in different phases
homogeneous catalyst
reactants & catalysts in the same phase
homogenous catalysts are often ______ and can be used at ______
acids
1 atm
enzymes
biological catalysts
enzymes use…
(r/t TD)
coupling
causes catalysis to plateau
saturation
