Chapter 15 Flashcards
Rate of a chemical reaction
how fast the reaction occurs
rate =
change in the amounts of reactants or products/ change in time
Rate for reactants is (+ or -) because …
negative becuase they decrease as the reaction continues
Rate for products is (+ or -) because …
postive becasue they increase as the reaction continues
Find the rate of:
aA + bB -> cC +dD
-1/a (delta [A]/delta t) = -1/b (delta [B]/delta t) = +1/c (delta [C]/delta t) = +1/d (delta [D]/delta t)
Rate law for zero order and list all of the factors of it
k[A]0 = k
- units M/s
- independent of the concentration of A
- concentration of reactant decreases linearly with time
- slope of a line is constant because the rate does not slow does as the concentration of A decreases
- rate of the reaction is the same at any concentration
Rate law for first order and list all of the factors of it
k[A]1
-units: 1/s
-rate is directly proportional to the concentration of A
- rate slows down as reaction proceeds because concentration of reactants decreases
Rate law for second order and list all of the factors of it
k[A]2
- units 1/M s
- rate is proportional to the square of the concentration
- curve flattens out more quickly
initial rate
the rate for a short period of time at the beginning of the reaction
- its directly proportional to the initial concentration
integrated rate law
a relationship between the concentration of the reactants and time
first order integrated rate law
ln[A]t = -kt + ln[A]0
Second order integrated rate law
1/[A]t = kt + 1/[A]0
Zero order integrated rate law
[A]t = -kt + [A]0
half life (t 1/2)
the time required for the concentration of a reactant to fall to one half of its initial value
first order reaction half life
t 1/2 = ln 1/2 / k
second order reaction half life
t 1/2 = 1/k[A]0
zero order reaction half life
t 1/2 = [A]0/ 2k
Activation Energy (Ea)
an energy barrier or hump that must be surmounted in order for the reactants to transform into products
Frequency factor (A)
the number of times that the reactants approach the activation barrier per unit time
higher the activation energy
slower the reaction rate
reactant molecules
must collide in a specific way that allows for necessary bonds to break and form
reaction mechanisms
the series of individual chemical step by which an overall chemical reaction occurs
reaction intermediate
went from product to reactant
finding k and what is its unit
rate/ [A]
unit: 1/s
finding n
rate 2/ rate 1 = k[A]n/ k[A]n *log both sides
from: aA + bB -> cC +dD
find the overall order
rate =k [A]m [B]n
m+n= overall order
Graph for integrated first order
y axis: ln[A]t
x axis: time
slope: k
graph for integrated second order
y axis: 1/[A]t
x axis: time
slope: k
graph for integrated zero order
y axis: [A]t
x axis: time
slope: -k
Calculating activation energy
ln k2/k1 = Ea/R (1/T1 - 1/T2)
catalyst
went from reactant to product
