ch. 15 Flashcards
factors that affect reaction rate
- properties of reactants and products
- ability of reactants to contact each other
- concentrations
- temperature
- catalysts
how do properties of reactants and products affect reaction rate
acid/base, ppt reaction, etc
how does conc. affect reatction rate
higher conc. = more collisions = faster rate
lower conc. = less collisions = slower rate
how does temp affect reaction rate
higher temp = more collisions (faster cules with more energy) = faster rate –> more cules w suffiecient energy
lower temp = less collisions = less cules w sufficient energy to overcome Ea
how do catalysts affect reaction rate
speed up reaction by offering an alternate pathway with a lower Ea
inhibitor slows down reactions
rate law
rate = k[A]^n
finding rate law
rate2/rate1 = conc2/conc1
how to find order of reaction when the reactions are complicated
you can get a pseudo order
increase the concentration of everything but the species of interst
makes changes in conc of everything else negligible
integrated rate law vs differential rate law
concentrations depend on time
half life
time required for conc. to decrease by 1/2
for first order, half-life time is
constant
for second order half life time
becomes longer with time
zero order
rate doesn’t depend on conc.
like first order, graph slope =-k
for zereo order, half life time
becomes shorter over time
enzyme reactions are what order
zero order
if a reaction is 2nd order, what graph axes will yield a linear plot
1/[A] vs. time
collision theory
rate of reaction is proportional to the # of effective collisions
effective collisions consist of 2 thngs
1. enough energy
2. proper orientation
exothermic energy diagrams –> describe
delta H = -
heat released
reactants higher than products
for reverse reaction Ea, Ea = delta H + Ea forwards rxn
endothermic energy diagram
heat absorbed
delta H = +
reactants less than products
what does the top of a energy diagram symbolize
transition state
high energy + unstable
arrhenius equation
k = Ae^(-Ea/RT)
describe the variables
k = rate constant
A = frequency factor
Ea = activation enrgy
R = 8.3145
T = K
mechanisms
most reactions don’t occur in a single step
mechanism is a series of elementary steps
sum of elementary steps gives overall reaction
mechanism agrees w rate law
first order reaction can also be called
second order
third order
unimolecular
bimolecular
termolecular
what step of a mechanism is used to construct the rate law
slow step
