5.111 Lecture Summary #31 Wednesday, November 26, 2014
Reading for Today: 14.6, 17.7 in 5th ed and 13.6, 17.7 in 4th ed.
Reading for Lecture #32: 14.7-14.8, 14.10 in 5th ed and 13.7-13.8, 13.10 in 4th ed
Topic: Kinetics
I. Radioactive Decay
II. Second Order Integrated Rate Laws
III. Relationship Between k and K
IV. Elementary Steps and Molecularity
I. Radioactive Decay is an example of a first order process. Current research includes
topics ranging from nuclear waste storage to designing new radioactive tracers for use in
medicine. MIT Chemistry Professor Alan Davison was a patent holder of CardioliteTM,
which uses Technetium-99 for diagnostic organ imaging and bone scans.
The decay of a nucleus is of the number of surrounding
nuclei that have decayed. We can apply first order integrated rate laws:
[A] = [A]0 e-k t and t1/2 = 0.6931
k
However, instead of concentration, the first order integrated rate law is expressed in terms
of N (number of nuclei)
N = Noe-k t k is the decay constant
t is time
N0 is the number of nuclei originally present
Chemical kinetics – monitor changes in o ver time
Nuclear kinetics – monitor rate of occurrence of events with a
Geiger counter (radiation detector)
Decay rate is also called Activity (A)
Activity = A = -dN = k N
dt
because activity is proportional to the number of nuclei (N):
N = Noe-k t can be expressed as A = Aoe-k t A is Activity
A0 is original activity
Units
S.I. unit for Activity is the becquerel (Bq) 1 Bq = 1 radioactive disintegration per second
Older unit is the curie (Ci) 1 Ci = 3.7 x 1010 disintegrations per sec
1
Reading for Today: 14.6, 17.7 in 5th ed and 13.6, 17.7 in 4th ed.
Reading for Lecture #32: 14.7-14.8, 14.10 in 5th ed and 13.7-13.8, 13.10 in 4th ed
Topic: Kinetics
I. Radioactive Decay
II. Second Order Integrated Rate Laws
III. Relationship Between k and K
IV. Elementary Steps and Molecularity
I. Radioactive Decay is an example of a first order process. Current research includes
topics ranging from nuclear waste storage to designing new radioactive tracers for use in
medicine. MIT Chemistry Professor Alan Davison was a patent holder of CardioliteTM,
which uses Technetium-99 for diagnostic organ imaging and bone scans.
The decay of a nucleus is of the number of surrounding
nuclei that have decayed. We can apply first order integrated rate laws:
[A] = [A]0 e-k t and t1/2 = 0.6931
k
However, instead of concentration, the first order integrated rate law is expressed in terms
of N (number of nuclei)
N = Noe-k t k is the decay constant
t is time
N0 is the number of nuclei originally present
Chemical kinetics – monitor changes in o ver time
Nuclear kinetics – monitor rate of occurrence of events with a
Geiger counter (radiation detector)
Decay rate is also called Activity (A)
Activity = A = -dN = k N
dt
because activity is proportional to the number of nuclei (N):
N = Noe-k t can be expressed as A = Aoe-k t A is Activity
A0 is original activity
Units
S.I. unit for Activity is the becquerel (Bq) 1 Bq = 1 radioactive disintegration per second
Older unit is the curie (Ci) 1 Ci = 3.7 x 1010 disintegrations per sec
1
