Question

35. Strotium−90, a radioactive isotope, is a major product of an atomic bomb explosion. It has a half-life of 28.1 yr. (a) Calculate the first-order rate constant for the nuclear decay. (b) Calculate the fraction of 90Sr that remains after 10 half-lives. (c) Calculate the number of years required for 92.3 percent of 90Sr to disappear. (a) yr−1 (b) × 10 (c) × 10 yr

The activity of a radioactive sample is the number nuclear disintegrations per second, which is equal to the first-order rate constant times the number of radioactive nuclei present. The fundamental unit of radioactivity is the curie (Ci), where 1 Ci corresponds to exactly 3.70 × 1010 disintegrations per second. This decay rate is equivalent to that of 1 g of radium−226. The molar mass of Ra−226 is 226.03 g/mol. Calculate the rate constant for the radium decay. × 10 s−1 (Enter your answer in scientific notation.) Calculate the half-life for the radium decay. × 10 s (Enter your answer in scientific notation.) Starting with 2.6 g of the radium sample, what is the activity after 3.0 × 102 yr? Ci

Answer #1

The half-life of a dangerous radionuclide, strontium-90,
90Sr, is 29 years. This isotope is produced during the
nuclear fission reactions of atomic power reactors; if a receptor
is compromised (at Chernobyl and Fukushima it happened)
considerable amounts can be released. It has yet to be disclosed
how much 90Sr was released at Fukushima (the authorities
won't say, though perhaps they don't know), so let's just suppose
9.0 g (possibly a gross underestimate).
a. Please find the rate constant for the...

The
radioactive isotope Gold-198 has a half-life of 64.80 hrs. A sample
containing this isotope has an initial activity of 40.0 μCi.
Calculate the number of nuclei that will decay in the time interval
from 10 hrs to 12 hrs.[10 marks]

The radioactive decay of thallium-206 to lead has a half-life of
4.20 min. Strarting with 5.10*10^22 atoms of thallium-206,
calculate the number of such atoms left after 42.0 ,in. Enter your
answer in scientific notation.

The Curie (Ci) is a unit of radioactivity named after Marie
Sklodowski-Curie and Pier Curie, it represents the activity of one
gram of the most stable isotope of radium 226Ra, or 3. 7
∗ 1010 decays per second. While Ci is not a SI unit, it
is commonly used by the US industries and government bodies. The
isotope has a half-life of about T1/2 ≈ 1600 years. Thus
the decay coefficient for 226Ra equals k = (ln
2)/T1/2 ≈ 4....

The radioactive isotope 198Au has a half-life of 64.8 hr. A
sample containing this isotope has an initial activity (t = 0) of
1.5x 10^12 Bq. Calculate the number of nuclei that decay in the
time interval between t1 = 10 hr and t2 = 12 hr.
Please show and explain work, and do not use calculus to solve
it.

Radioactive decay can be used to determine the age of an object.
If you know the number of radioactive nuclei with which an object
started, the number of radioactive nuclei currently present, and
the half-life of the isotope, you can calculate the time since the
object was created.
Suppose an object was created with 3.270×109 nuclei of a
particular isotope that has a half-life of 1.66×103 yr.
At this point in time 1.079×109 nuclei of this
particular isotope remain. What...

The radioactive plutonium isotope, 239Pu, has an half-life of 24
100 years and undergoes alpha decay. The molar mass of 239Pu is
239.0521634 amu. The sample initially contains 10.0 g of 239Pu.
(a) Calculate the number of moles of 239Pu that are left in the
sample after 15 000 years. (4)
(b) Determine the activity of 239Pu after 15 000 years, in units
of Bq.

The radioactive plutonium isotope, 239Pu, has an
half-life of 24 100 years and undergoes alpha decay. The molar mass
of 239Pu is 239.0521634 amu. The sample initially
contains 10.0 g of 239Pu. (a) Calculate the number of
moles of 239Pu that are left in the sample after 15 000
years. (4) (b) Determine the activity of 239Pu after 15
000 years, in units of Bq.

BIOPHYSICS
1. Cobalt-60 (60Co), is a synthetic radioactive
isotope of cobalt with a half-life of 5.2713 years. It is an
isotope that emits gamma rays essential to the medical community
for cancer treatments, as well as sterilization of medical devices.
Cobalt-60 is used as a radiation source for medical radiotherapy
where it is used in cancer treatment to control or kill malignant
cells. Cobalt-60 is used as the radiation source in Gamma Knife
equipment that enables non-surgical treatment of brain...

1. What is the age (in y) of mummified primate skin that
contains 9.49% of the original quantity of 14C? (The half-life of
14C is 5715 years.)
_____________ y
2. The integrated form of the first-order rate law of nuclear
decay is expressed as follows.
−λt = ln(N_t / N_0)
In this equation, λ is the decay constant, t
is time, Nt is the number of nuclei
remaining at time t, and No is the
original number of nuclei present....

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