Exam 3 (kinetics and equilibrium) Flashcards
Homogenous vs. heterogenous rxns
homo: all of the species within the reaction are in the same phase
hetero: all the species within the reaction are not in the same phase
Are solids and liquids included in the Kc expression? Why?
No; their associated pressure remains the same at a particular temperature
How to find Kp given Kc
Kp= Kc [(RT)prod/(RT)react]
*# moles (RT)prod/ # moles (RT)react
*moles are the same, then Kp=Kc
How to find Knet:
a. two separate steps
b. reverse direction
c. coefficients multiplied
a. (k1)(k2)= Knet
b. (1/k)
c. K^n ; n=coefficient multiplier
Exothermic rxn:
- what will an increase in temp do to a rxn in equilibrium
a. increase temp, shift to the left, less product & more reactant, K will decrease
Endothermic reaction:
- what will an increase in temp do to a rxn in equilibrium
a. increase temp, shift to the right, more products & less reactants, k increases
How does pressure affect equilibrium?
increasing pressure will shift rxn to the side with less moles
decreasing pressure will shift rxn to the side with more moles
moles on both sides of rxn are equal will mean no change
How does concentration affect equilibrium?
increasing concentration will shift rxn in opposite direction
decreasing concentration with shift rxn in the same direction
How does ph affect equilibrium?
increasing acid concentration will decrease ph (more acidic)
decreasing acid concentration will increase ph (more basic)
How does increasing pressure and decreasing volume affect equilibrium?
will shift to side with less moles;
K is affected.
K will decrease if shifting to reactants
K will increase if shifting to products.
How does decreasing pressure and increasing volume affect equilibrium?
will shift to the side with more moles; K is affected.
K will increase if shifting to products side
K will decrease if shifting to reactants side
what happens to Q when reactants are added?
Q decreases, so the equilibrium shifts to produce more products
what happens to Q when products are added?
Q increases, so the equilibrium shifts to produce more reactants
if Q < K, then…
the reaction is not at equilibrium and will make more products at the expense of reactants
if Q >K, then…
the reaction is not at equilibrium and will make more reactants at the expense of products
A. When K > 1
B. When K < 1
C. When K=1
A. favors products
B. favors reactants
C. is at equilibrium
The ways a rate of rxn can be followed are?
Temp, pressure, weight (sedimentation), color and ph
What is kinetics
how fast a reaction proceeds and the detailed mechanism involved for each of the step(s) involved as the reaction proceeds from reactants to products
How to find average rate?
[final] - [initial] / Tf - Ti
Instantaneous rate?
the same as average but is specific to a moment in time
When will instantaneous rate be the fastest?
at the beginning of a reaction, when t=0
First order equation
ln(At) - ln(Ao) = -kt
At=Ao e^-kt
-kt = slope and ln(Ao)= c
First order graph (concentration vs. time)
negative slope
second order equation
1/At - 1/Ao = kt
or
1/At= 1/Ao + kt
second order graph (concentration vs. time)
first order graph (rate vs. concentration)
positive slope
second order graph ( rate vs. concentration)
positive slope
zero order graph (rate vs. concentration)
zero order graph (concentration vs. time )
second order graph ( 1/concentration vs. time)
zero order equation
[A]= [Ao] - kt
temperatures effect on rxn?
higher temp , larger K, faster the rate of rxn
frequency of collision/collision frequency affect on rxn?
increase in the frequency of collisions, increases rate of rxn
collision frequency increases with concentration
kinetic energy of the collisions/collision energy affect on rxn?
K.E increases with an increase in temp
activation energy affect on rxn?
smaller Ea , larger K.e, larger the K, faster the rate
what does the collision theory say rate of rxn depends on?
energy of collisions and the orientation of colliding molecules
Arrhenius equation
k= Ae^-Ea/RT
lnk2 -lnk1= - Ea/R (1/T2 - 1/T1)
k= rate constant
A= Arrhenius/collision factor
R= Gas constant
- only affected by temp
A=pZ ; Z= collision frequency, p= ratio of orientated collisions out of all possible collisions
what does the Arrhenius equation do?
it accounts for the collision frequency, kinetic energy, orientation, and concentration of molecules in a reaction.
