Question

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.

Answer #1

Solution :

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 activity of a sample containing radioactive Ag-108 is
6.4×10^4 Bq. Exactly 12 min later, the activity is 2.0×10^3 Bq.
Calculate the half-life of Ag-108. Calculate the initial number of
Ag-108 nuclei in the sample.

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 sample of radioactive nuclei initially contains 6.00
×1010×1010 radon atoms. The half-life of this type of nucleus is
500 days. How many nuclei have decayed after 167 days?
A sample of radioactive nuclei initially contains
6.00 radon atoms. The half-life of this type of nucleus
is 500 days. How many nuclei have decayed after 167 days?
2.00×1010
4.00×1010
1.24×1010
4.76×1010

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.

A sample of radioactive nuclei initially contains 9.00 ×1010
radon atoms. The half-life of this type of nucleus is 450 days. How
many nuclei have decayed after 150 days?
OPTIONS:
7.14×1010
6.00×1010
3.00×1010
1.86×1010

The half-lives in two different samples, A and B, of radioactive
nuclei are related according to
T1/2,B =
1
4
T1/2,A.
In a certain period the number of radioactive nuclei in sample A
decreases to one-eighth the number present initially. In this same
period the number of radioactive nuclei in sample B decreases to a
fraction f of the number present initially. Find
f.

The half-lives in two different samples, A and B, of radioactive
nuclei are related according to T1/2,B = 1 6 T1/2,A. In a certain
period the number of radioactive nuclei in sample A decreases to
one-fourth the number present initially. In this same period the
number of radioactive nuclei in sample B decreases to a fraction f
of the number present initially. Find f.
(its not 1/3.. its not 0.917... and its not .875) Please answer
to 4 decimal places

Initially a sample of radioactive nuclei of type A contains 4
times as many nuclei as a sample B. 2 days later the samples both
have the same number of nuclei.
Which sample has the longer half life?
Determine the half life of B if the half life of A is 0.5
days.

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