Exam 2 Flashcards
what is the driving force behind a spontaneous reaction?
motional freedom of particles increasing
during a spontaneous chemical reaction, it is found that the change in Ssys is less than 0. what does this mean?
the change in Ssurr is greater than 0 and its magnitude is greater than the change in Ssys
when is a process always spontaneous?
change in H<0 and change in S>0
second law of thermodynamics
the entropy of a universe increases in any spontaneous reaction
third law of thermodynamics
entropy of a perfect crystal at absolute zero is 0 while W=1
provides a baseline/refrence for entropy
microstates
unique distribution of particles among energy levels
how does entropy affect spontaneity?
S<0 less spontaneous
more spread out means its more spontaneous
what factors affect reaction rates?
- physical state of reactant
- concentration of reactants
- temperature
- presence of a catalyst
enthalpy
change in heat
three types of motion
translational, vibrational, rotational
how does temperature influence spontaneity?
higher temperature means increase in collisions, therefore higher spontaneity
integrated rate law
change in concentration of a reactant with time
units for 0th order
M/s
units for 1st order
1/s
units 2nd order
1/Ms
activation energy
minimum energy needed to break bonds in reactants and form bonds in the products
transition state/activation complex
high energy transition state
peak
reaction mechanisms
set of steps that describe how a reaction occurs at the molecular level
rate-determining step
slowest step in the reaction
homogeneous catalyst
catalyst in the same phase as the reactants
heterogeneous catalyst
catalyst in a different phase from the reactants
catalysts
not consumed, speeds up reaction, lowers activation energy
what must happen for a reaction to occur?
- molecules must collide
- must exceed the threshold energy
- must collide with proper orientation
how does a lower energy affect a spontaneous reaction?
makes it more stable
what is energy distribution affected by?
molecular motion and volume
energy state/level
allowed value of energy
w
number of microstates
is motion a type of kinetic energy?
yea
what increases with temperature?
motion
how do exothermic reactions affect their surroundings?
have the possibility to increase the entropy of their surroundings
what is the energy change of a reversible process?
no net flow of energy between the system and the surroundings
what does the entropy change experienced by the surroundings of a chemical thermodynamic system depend on?
whether the process is exothermic or endothermic
what remains constant with Gibbs free energy?
temp and pressure
if something is spontaneous what is the change in G of the system equal to?
less than 0
what does a reaction rate depend on?
concentration
what happens to the reaction rate as the concentration decreases?
the reaction rate decreases
how are exponents in a rate law determined?
experimentation only
does the rate constant depend on the concentration of the reactants?
nah
what controls the reaction rate in a pseudo-first-order reaction?
concentration of the limiting reactant
pseudo-first-order
all reactants but one are present at such high concentrations that they don’t decrease significantly during the reaction
zero order
rate of reaction is independent of concentration
3rd order units
1/M2s
rate law for 0 order
rate=k
which order has 1/something
second order
how does a larger value of W affect entropy?
more entropy!!
