Question

A radioactive isotope has a half-life of 72.0 min. A sample is
prepared that has an initial activity of 1.40×10^{11}
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?

Answer #1

The
radioactive nuclide Plutonium-199 has a half-life of 43.0 min. A
sample is prepared that has an initial activity of 7.56 ×1011 Bq.
i. How many Plutonium-199 nuclei are initially present in the
sample?
ii. How many are present after 30.8 min?
iii. What is the activity at this time?

A radioactive sample contains 2.94 μg of pure11C, which has a
half-life of 20.4 min.
a) How many moles of 11C is present ini- tially? The value of
Avogadro’s number is
6.02 × 1023 nuclei/mol. Answer in units of mol.
b) Find the number of nuclei present initially. Answer in units
of nuclei.
c)Find the initial activity of the sample. Answer in units of
Bq.
d)Find the activity of the sample after 6.97 h. Answer in units
of Bq.

The radioactive isotope 198Au has a half-life of 64.8 hours. A
sample containing this isotope has an initial activity at (t=0) of
1.50e-12 Bq. Calculate the number of nuclei that will decay in the
time interval between t1=10 hours and t2=20 hours
Answer is 4.60e16 but I'm not sure how. Thanks and please show
work

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.

The radioactive isotope 234Pa has a half-life of 6.70
h. A sample containing this isotope has an initial activity
(t = 0) of 35.0µCi. Calculate the number of nuclei that
decay in the time interval between t1 = 7.0 h
and t2 = 14.0 h.
___________ Nuclei

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]

A freshly prepared sample of a certain radioactive isotope has
an activity of 10.4 mCi. After 4.20 h, its activity is 8.00
mCi.
(a) Find the decay constant and half-life. decay constant s-1
half-life h
(b) How many atoms of the isotope were contained in the freshly
prepared sample?
(c) What is the sample's activity 33.7 h after it is prepared?
mCi

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.

A radioactive isotope has an activity of 8.58×104 Bq initially.
After 3.85 hours the activity is 5.15×104 Bq. What is the half-life
of the isotope? Tries 0/20 What is the activity after an additional
3.85 hours?

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