Chem 1B
Dr. White
Worksheet 26: Nuclear Chemistry Key
1.
2.
Select the nuclide that completes the following nuclear reaction.
Select the nuclide that completes the following nuclear reaction.
3.
Select the nuclide that completes the following nuclear reaction.
4.
Select the nuclide that completes the following nuclear reaction.
5.
Select the nuclide that completes the following nuclear reaction.
6.
Select the nuclide that completes the following nuclear reaction.
7.
Select the nuclide that completes the following nuclear reaction.
8.
Select the nuclide that completes the following nuclear reaction.
Chem 1B
9.
Dr. White
Write a complete, balanced equation to represent the alpha decay of radon-210.
10.
Write a complete, balanced equation to represent the electron capture decay of argon-37.
11.
Write a complete, balanced equation to represent the formation of manganese-55 by the beta
decay of another nuclide.
12.
A bottle of vintage red wine has lost its label. The concentration of tritium (
) in the wine is
0.34 times that found in freshly bottled wines. If the half-life of tritium is 12.3 years, estimate the
time elapsed since the wine was bottled.
ln 2
k
ln 2
k=
= 0.0564yr −1
12.3yr
N
ln
= −kt
N0
ln 0.34
t=
= 19.1years
−0.0564yr −1
t1/ 2 =
€
13. Polonium-210 has a half-life of 138.39 days. Suppose 1 gram of Po-210 was used to poison
Alexander Litvenenko (a fugitive officer in the Russian Secret Service who was murdered by radiation
poisoning). How many days will have passed if 1/64th of the original sample still remains?
ln 2
k
ln 2
k=
= 0.00500865days −1
138.39days
N
ln
= −kt
N0
ln(1/64)
t=
= 830.34days
−0.00500865days −1
t1/ 2 =
€
Chem 1B
Dr. White
14. All isotopes of technetium are radioactive, but they have widely varying half-lives. If an 800.0 gram
sample of technetium-99 decays to 100.0 g of technetium-99 in 639,000 years, what is its half-life?
N
= −kt
N0
N
1
100.0g
1
k = ln
× = ln
×
= 3.254 x10 −6 years −1
N 0 −t
800.0g −639,000years
ln 2
t1 / 2 =
k
ln 2
t1 / 2 =
= 2.13x10 5 years
−6
−1
3.254 x10 years
ln
15. A 208 g sample of sodium-24 decays to 13.0 g of sodium-24 within 60.0 hours. What is the halflife of this radioactive isotope?
€
N
= −kt
N0
N
1
13.0g
1
k = ln
× = ln
×
= 0.04621hrs −1
N 0 −t
208g −60.0hrs
ln 2
t1/ 2 =
k
ln 2
t1/ 2 =
= 15.0hrs
0.04621hrs −1
ln
€
16. A living plant has a rate of decay of C-14 of 13.6 counts per minute per gram of C. How many
counts per minute per gram will be measured from a 15,000 year sample? The half life of C-14 is
5730 years.
ln 2
k
ln 2
t1 / 2 =
= 1.2097x10 −4 yrs
−1
5730yrs
N
ln
= −kt
N0
N
ln
= −1.2097x10 −4 yrs(15,000yrs)
13.6 counts min -1 g −1
N
ln
= −1.815
13.6 counts min -1 g −1
N
= 0.163
13.6 counts min -1 g −1
t1 / 2 =
N = 2counts min -1 g −1
€
Chem 1B
Dr. White
17. A living plant has a rate of decay of C-14 of 13.6 counts per minute per gram of C. How old is a
petrified tree that was found to give 1.2 counts per minute per gram? The half life of C-14 is 5730
years.
ln 2
k
ln 2
t1 / 2 =
= 1.2097x10 −4 yrs
−1
5730yrs
N
ln
= −kt
N0
N
1
ln
×
=t
N 0 −k
1.2
1
ln
×
13.6 −1.2097x10 −4 yrs
1
−2.427 ×
= 2.01x10 4 yrs
−1.2097x10 −4 yrs
t1 / 2 =
€