C11. Chemical kinetics

Question 1

what is kinetics?

Answer 1

Kinetics is the study of the rates of reaction and can tell us how
quickly components react with each other, how fast components
decay and how this is affected by temperature

Question 2

what is the rate of reaction?

Answer 2

The rate of reaction is the rate of change of the concentration of
either the products (P) or reactants (A)

Question 3

rate of formation (products) equation?

Answer 3

d[P] / dt

Question 4

rate of loss (reactants) equation?

Answer 4

d[A] / dt

Question 5

Rate directionally proportional?

Answer 5

Rate directionally proportional to [A][B]

Question 6

k?

Answer 6

rate constant

Question 7

rate law?

Answer 7

ONE NOTE

Question 8

Describe zero order reaction? equation?

Answer 8

-The rate of disappearance of a reagent is constant and does not
depend on its concentration.
-rate of loss of reactant A= -d[A] / dt =k
-by integrating the expression, we get [A]= -kt + [A]0

Question 9

Describe plotting zero-order reactions

Answer 9

▪ Plot concentration (y) vs time (x).
▪ If you get a straight line your reaction is zero-order
▪ Slope = - k (mol dm-3 s
-1)
ONE NOTE

Question 10

Describe first order reactions? equations?

Answer 10

-The rate of disappearance of a reagent is proportional to the amount
of material remaining
-Rate of loss of reactant A = −d[A] / dt = k[A]
-By integrating the expression, we get: [A]t = [A]0 e to the power of -kt

Question 11

describe the concentration time graph of a first order reaction

Answer 11

Because a first-order reaction is an
exponential function, if we plot [A] vs. time we get an exponential decay
ONE NOTE

Question 12

Describe straight line graphs of first order reactions

Answer 12

-If you plot the ln[concentration] (y) vs time (x) and you get a straight-line your reaction is First-order
-ln(x) is dimensionless, it has no units.
-Slope = - k (s-1)
ln[A]t = ln [A]0 - kt
ONE NOTE

Question 13

what is half life? equation?

Answer 13

The half-life is the time taken for half the concentration of reactant to decompose.
EQUATION ON ONE NOTE

Question 14

T=

Answer 14

1/ k

Question 15

how does temp change rate?

Answer 15

As temperature increases,
more molecules have sufficient
energy to overcome the
activation energy barrier

Question 16

for two molecules to react they must…

Answer 16

1) Collide
2) Have sufficient energy to overcome Ea

Question 17

F=?

Answer 17

-Collision rate (z) is linearly dependent on temperature. However, the
fraction of molecules (F) having sufficient energy to overcome Ea
is exponentially dependent on temperate
F= e to the power of -Ea/ RT
R = Gas constant (8.314 J K-1 mol-1)
T = Temperature (K)

Question 18

k=?

Answer 18

k= Ae to the power of -Ea/ RT
by integrating the equation we get:
ln(k) = -Ea/ RT + ln(A) which is the integrated form of the Arrhenius equation

Question 19

how to find activation energy?

Answer 19

-by using integrated Arrhenius equation plot a straight line of ln(k) (y) vs 1/T(x) we can find the activation energy for a particular chemical process.
-slope = -Ea / R (Jmol-1)
ONE NOTE

Question 20

how to predict the rate of degradation? equation?

Answer 20

ONE NOTE

Question 21

What are parallel reactions

Answer 21

Parallel reactions involve
the decay of a compound into
two (or more) products at
different rates.
ONE NOTE

Question 22

What are consecutive reactions?

Answer 22

Consecutive reactions can
involve a series of
intermediates which then go
on to form products.

Question 23

what is the rate-determining step

Answer 23

The slowest rate within a
consecutive reaction is the
rate-determining step. The
reaction cannot go faster than
the rate of the slowest step

Question 24

Describe reactions in equilibrium

Answer 24

d[A]/ dt = d[P]/dt
kfor[A] = krev[P]
ONE NOTE

Question 25

Keq=

Answer 25

[P] / [A]
Products dominate Keq&raquo_space; 1
Reactants dominate Keq &laquo_space;1
At equilibrium Keq = 1

Question 26

At equilibrium ΔG =?

Answer 26

0
ONE NOTE

Question 27

A reaction is spontaneous if…

Answer 27

Keq&raquo_space; 1 (reaction favours the products)

Question 28

ΔG°=

Answer 28

ΔG° = -RTlnKeq
ONE NOTE

Question 29

Keq in terms of ΔG =?

Answer 29

e to the power of (-ΔG/ RT)

Question 30

Describe Van’t Hoff equation

Answer 30

one note