Rates Flashcards
(19 cards)
definition of rate of reaction? what are the units?
the amount of product formed per unit volume per unit time (mol dm-3 s-1)
what is the rate equation?
Rate=k[A]0[B]1[C]2
describe first order
if [B] is changed, the rate is changed by the same amount (directly proportional on a graph)
how do you calculate overall order?
simply add up all the orders
describe second order
if [C] is changed, the rate is changed by a squared relationship (curve on a graph)
describe zero order
if [A] is changed, rate is unaffected (straight horizontal line on a graph)
how can you find out the order of a reaction?
plot a graph of rate against [concentration] and analyse the shape
what practical’s are done to determine rate?
disappearing cross (initial), gas syringe (continuous), iodine clock
how do you rearrange to find k?
rate/[A][B][C]
what are units the same for?
k and rate
how do you determine k from a graph if first order?
find the gradient as k would be m in y=mx+c OR use half life
definition of half life
the time taken for the concentration of a reactant to decrease to half its original value
when are concentration-time graphs used?
for continuous monitoring methods
how do you use half life to determine an order?
a constant half life indicates first order (use any two)
what is the equation to find k from half life?
k=ln2/half life value
in a multi-step reaction, which is the rate determining step (RDS)?
the slowest step
what is the definition of order?
the number of molecules of that reactant in the r.d.s
the catalyst is not in the _____ equation but is in the ______ equation
chemical
rate
what do the steps in the mechanism add to?
the balanced equation
