kinetics Flashcards
define rates of reactions
rate of chemical reaction is defined as the change in concentration per unit of time
state general rate law formula
rate = k[A]^m[B]^n
what determine overall order of reaction
sum of m+n
describe method of initial rates
put rates over each other, cross cancel and find m and n
what is half life
Half life is the time required for a reactant to reach half of its original concentration
state the 3 formulas for first order reaction
rate = k[A] ln[A]= -kt + ln[A]initial t1/2 = ln2/k
state the 3 formulas for second order reaction
rate = k[A]^2 1/[A]= kt + 1/[A]initial t1/2= 1/k[A]initial
state the 3 formulas for zero order reaction
rate = k [A]= -kt + [A]initial t1/2 = [A]initial/2k
what does a reaction mechanism consist of
a series of elementary steps, sum = overall reaction
mechanism must agree with experimentally determined rate law * must test if plausible
what is temperature
describes random motion of particles in a substance
increasing temp =
increasing rate of chemical reaction
what is activation energy (Ea)
barrier that needs to be overcome for a reaction to occur
state the 2 collision formulas
ln(k) = -Ea/R 1/T + ln (A)
ln(k2/k1) = Ea/R (1/T1 - 1/T2)
R=8.3145 J/kmol
what is a catalyst
a substance that speeds up a reaction without being consumed itself ☆ lowers the Ea
name the 2 types of catalyst
homogenous
heterogenous
describe homogenous catalysts
presents in same phase as reacting molecules
ex: enzymes are nature”s catalysts
describe heterogenous catalysts
exists in a different phase usually solid
ex: hydrogenation is a reaction that is catalyzed by a metal surface
what are reaction mechanisms
series of steps involved in the conversion of reactants to products
rate of elementary steps is determined by their molecularity (number of species which must collide for the reaction to occur)
slowest step = RATE DETERMINING STEP
what does kinetics of radioactive decay follow
first order kinetics
when do zero order reactions occur
Occur when enzymes or metal surfaces are involved in the reaction
