Question

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.

Answer #1

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 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?

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.

15.58 The half-life for the radioactive decay of C−14 is 5730
years. How long will it take for 25% of the C−14 atoms in a sample
of C−14 to decay? If a sample of C−14 initially contains 1.9 mmol
of C−14, how many millimoles will be left after 2250 years?

The half-life for the radioactive decay of C−14 is 5730
years.
Part A: How long will it take for 25% of the C−14 atoms in a
sample of C−14 to decay?
Part B: If a sample of C−14 initially contains 1.9 mmol of C−14,
how many millimoles will be left after 2255 years?

The gold nucleus Au(198,79) undergoes alpha decay with a
half-life of 2.70 days.
A. ) Find how many neutrons and protons are in the
daughter nucleus produced by this decay.
B.) Find the activity in Bq (decays/sec) of a sample that
contains 5.0 grams of Au(198,79) nuclei.
C.) A 2.5 kg suitcase at an airport absorbs 2.0 × 10−3 J/kg from
100 keV x-rays. How many photons are absorbed?

The radioactive isotope thorium 234 has a half-life of
approximately 578 hours.
If a sample has an initial mass of 64 mg, a function that models
the mass in mg after t hours is a(t) =
The initial mass will decay to 12 mg after ______ hours
Radioactive decay equation:
a(t) = a0⋅2 ^ (−t / h)
a0 = starting amount
a(t) = amount after t hours
h = half life in hours

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?

Boron-12, an unstable nucleus, undergoes the following decay
process. The half-life for this beta decay is 20.2 milliseconds and
the atomic mass of Boron-12 is 12.0143521 u.
.a) What is the binding energy per nucleon for Boron-12? (5
pts)
.b) A 275 g sample of this isotope of Boron contains how many
nuclei? (1 pt)
.c) If you started with a 275 g sample of Boron-12 at time t =
0, how many nuclei of this isotope would be left...

Complete the table for the radioactive isotope. (Round your
answers to two decimal places.)
Isotope
Half-life
(in years)
Initial
quantity
Amount after
1000 years
Amount after
10,000 years
239Pu
24,100
?grams
grams
?0.4 grams

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