Chemical Kinetic and Equilibrium Flashcards
what is the rate law?
rate = K[A]^x[B]^y
where x and y are coefficients of reactants A and B
K = rate constant
what is the overall rate of rxn?
x+y
determined experimentally
zero order rxn?
constant rate
independent of conc of reactants
first order rxn?
what;s an example of first order?
rate is proportional to conc of 1 reactant
half life
2nd order
K[A]2 or K[A][B]
mixed order
fractional order (fractional exponent)
what is the collision theory of chem kinetics?
rate of rxn is proportional to numbe of collisions per sec
effective collision
collision of reactants that lead to formation of products
rate of collision r =
r = fz
f is fraction of effective collisions
z is # of collisions
transition state
mcules that collide with enough E go into transition state, bonds are weakened, new bonds begin to form
what factors influence rxn rate?
- conc of reactants…higher conc is high rate
- temp…higher temp is higher rate
- medium…change medium, change rate
- catalyst…rate inc, Ea dec
homogenous vs heterogeneous catalysts
homo-same phase as reactants
hetero-different
forward rxn rate
reverse rxn rate
Eq. constant, Kc =
Rf = Kf[A]x Rr = Kr[B][C]
Kc = Kf/Kr
what is the law of mass action?
aA + bB –> cC + dD
rxns with more than 1 step:
Keq = [C]c[D]d/[A]a[B]b
[Products]/[reactants]
what is reaction quotient Q?
measure of the degree to which rxn has gone to completion
Q=Kc at eq
what are the characteristic of Keq?
Pure solids and liquids not in the expression
Is given for a given system of given T
If Keq is larger than 1, more products than reactants
If small, like .1, more reactants
If Keq ~ 1, same product and reactants
when P is system increases, which side will rxn shift?
side with less moles
If V increases in system, which way will rxn shift?
if V inc, P dec, so shift to side with more moles
In a zero order rxn, what does rate =?
rate = K!
Rate = K[A]^0 rate = K(1)
what is the half life equation?
1/2 = e^(-kt)
Take ln of each side
are catalysts consumed in a rxn?
no
does a catalyst change the Keq?
no
