FINAL - Chapter 8 Kinetics I

Question 1

What is the arrhenius equation? And the one for plot?

What does the A mean?

Answer 1

k = Ae^(-Ea/RT)
lnk = -Ea/R(1/T) + lnA

Frequency of collisions and the fraction of those collisions that result in a successful reaction

Question 2

How to derive the eqatuion for Arrenhenius with two temperatures

Answer 2

K1 k = Ae^(-Ea/RT)
K2 = k = Ae^(-Ea/RT)

Divide both, eliminates A bring up positive exponent

k1/k2 = e^-Ea/RT1 + Ea/RT2

Factor out Ea/R and then you get inside (1/T2-1/T1)

Question 3

Units for K

Answer 3

O order Ms^-1
1st order s^-1
2nd order M^-1S^-1
3rd order M^-2s^-1

Question 4

What causes 0 order kinetics?

Answer 4

Appears where another factor such as saturation where increasing concentration has no effect. Product of conditions, so doesn’t actually exist. 1st and 2nd order can appear as 0 under certain conditions

Question 5

Outline the collison theory

Answer 5

Arrhenuis

Only works in gaseous state

For a successful collision, molecules need to have correct orientation and kinetic energy greater or equal to the Ea of the reaction

The fraction of particles with this required Ea increases with temperature (maxwell-boltzmann curves)

Question 6

Integrated Rate Laws

0 order
1 order
2 order

Try to practice deriving them

Answer 6

0 order
[A]t = -kt + [A]0

1st order
[A]t = [A]0e^(-kt)
ln[A]t = -kt + ln[A]0

2nd order
-1/[A] = -kt + 1/[A]0

Question 7

Half Life Reactions

0 order
1st order
2nd order

To find the equation set [A]t = [A]0/2

Answer 7

0 order
[A]0/2k

1st order
ln2/k
(to derive remember it’s ln(1/2A) and to split it so ln(1/2) + ln(A)

2nd order
1/k[A]0
(get rid of minuses before deriving half life)

Question 8

Outline transition state theory

Answer 8

More complicated than collision theory , (eyring)

chemical reactions require that molecule must have
sufficient energy to reach a transition state
structure

The rate of chemical reaction depends on
1) concentration of transition state species
2) rate at which this species breaks apart
3) whether it breaks apart to form product or to reform reactants

Question 9

Limitations of collision theory (x3)

Answer 9

1) No collision in first theory so cannot explain this
2) A value can only be determined experimentally
3) Entropy is largely ignored (lumped into this A factor)

Question 10

How do you experimentally determine activation energy?

Answer 10

Measure rate constant at different temperatures, plot lnk vs 1/T, slope = -Ea/R and isolate for Ea

Question 11

Outline an Eyring plot

Answer 11

Measuring rate constant at different temperatures, plot lnk/T vs 1/T and slope is -−∆𝑯‡/R

Used to find activation enthalpy and entropy (with y intercept