Question

A certain radioisotope has a half-life of 8.96 days. What percentage of an initial sample of this isotope remains after 20 days?

Answer #1

A certain radioisotope has a half-life of 10.1 days. What
percentage of an initial sample of this isotope remains after 37
days?

For the isotope yttrium-91 (Z=39), the half-life is 58.5 days.
What percentage of an initial sample of yttrium-91 remains after
145 days?
Next question: A patient receives an absorbed dose of 0.120 mGy
from the neutron radiation with a relative biological effectiveness
of 18.0. What is the dose equivalent? Note: mGy=1.0 x 10^-3 Gy and
1.0mSv= 1.0 x 10^-3 Sv

1. Given that a freshly prepared radioactive isotope has a
half-life of 10 days, the percentage of it remaining after 30 days
is
A
30.0 %.
B
10.0 %.
C
12.5 %.
D
72.5 %.
2. During a second half-life, the original
material has decayed
A
25%.
B
50%.
C
75%.
D
100%.

Strontium-90 (90Sr) is a radioactive isotope with a half-life of
28.8 years. What percentage of this isotope remains after 11.4
years?

(a) Chromium-51 is a radioisotope that is used to assess the
lifetime of red blood cells The half-life of
chromium-51 is 27.7
days. If you begin with 32.8 mg
of this isotope, what mass remains after 70.6
days have passed? Since the decomposition is a
radioactive decay reaction, it is first order.
mg=
(b)What is the half-life of aluminum-25 if
19.2 seconds are required for the
mass of a sample of aluminum-25 to fall to
15.8 percent of its original...

A certain first order reaction has a half-life of 1.35 days.
What was the original concentration of the reactant if its
concentration after 5 days was found to be 0.0334 M? please show
all work

The half-life of 199Au is 3.14 days.
a.)Convert the half-life to units of seconds.
b.) What is the decay constant (in s−1) for this
isotope?
c.) Suppose a sample of 199Au has an activity of
0.360 µCi. What is this activity expressed in the SI unit of
becquerels (Bq)?
d.) Suppose a sample of 199Au has an activity of
0.360 µCi. What is this activity expressed in the SI unit of
becquerels (Bq)?
e.) Now suppose that a new sample...

Determining Half-Life. Measurements of the
radioactivity of a certain isotope tell you that the decay rate
decreases from 8520 decays per minute to 3800 decays per minute
over a period of 6.2 days. What is the half-life of this isotope?
Note that this is typically a good laboratory experiment to perform
in order to estimate half-life.
Half-life = days?

The unstable isotope 234Th decays by beta emission
with a half-life of 24.5 days.
a) What mass of 234Th will produce
9.9x1016 decays per second? (Note: 1u =
1.66x10-27 kg). Answer:1.2x10-4kg
b) If the initial decay rate of the sample is
9.9x1016 decays per second, what is the decay rate after
59 days? Answer: 1.4x1013kg decays/second
Must show all work to get to the answers I provided. Thank
you!

A radioactive isotope has a half-life of 72.0 min. A sample is
prepared that has an initial activity of 1.40×1011
Bq.
Q1: How many radioactive nuclei are initially present in the
sample?
Q2: How many are present after 72.0 min?
Q3: What is the activity after 72.0 min?
Q4: How many are present after 144 min?
Q5: What is the activity after 144 min?

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