Name: _________________________________
Half-life Practice Worksheet Part I
(Start with Column that is indicated by the arrow)
1. Sodium-24 has a half-life of 15 hours. How much sodium-24 will remain in an
18.0 g sample after 60 hours?
TIME
½ LIFE
MASS
2. After 42 days a 2.0 g sample of phosphorus-32 contains only 0.25 g of the
isotope. What is the half-life of phosphorus-32?
TIME
½ LIFE
MASS
3. Polonium-214 has a relatively short half-life of 164 seconds. How many
seconds would it take for 8.0 g of this isotope to decay to 0.25 g?
MASS
1
½ LIFE
Page
TIME
Name: _________________________________
4. How many days does it take for 16 g of palladium-103 to decay to 1.0 g? The
half-life of palladium-103 is 17 days.
TIME
½ LIFE
MASS
5. In 5.49 seconds, 1.20 g of argon-35 decay to leave only 0.15 g. What is the
half-life of argon-35?
TIME
½ LIFE
MASS
Half life = decay time ÷ # of half lives
6. The half-life of Cs-137 is 30.2 years. If the initial mass of the sample is
1.00kg, how much will remain after 151 years?
MASS
2
½ LIFE
Page
TIME
Name: _________________________________
7. Carbon-14 has a half-life of 5730 years. Consider a sample of fossilized
wood that when alive would have contained 24g of C-14. It now contains 1.5g.
How old is the sample?
TIME
½ LIFE
MASS
8. A 64g sample of Germanium-66 is left undisturbed for 12.5 hours. At the
end of that period, only 2.0g remain. What is the half-life of this material?
TIME
½ LIFE
MASS
Page
3
Half life = decay time ÷ # of half lives
Name: _________________________________
Solutions:
Half-life Practice Worksheet Part I
(Start with Column that is indicated by the arrow)
1. Sodium-24 has a half-life of 15 hours. How much sodium-24 will remain in
an 18.0 g sample after 60 hours?
TIME
½ LIFE
MASS
0
0
18
15
1
9
30
2
4.5
45
3
2.25
60
4
1.13
2. After 42 days a 2.0 g sample of phosphorus-32 contains only 0.25 g of the
isotope. What is the half-life of phosphorus-32?
TIME
½ LIFE
MASS
0
0
2
14
1
1
28
2
.5
42
3
.25
3. Polonium-214 has a relatively short half-life of 164 seconds. How many
seconds would it take for 8.0 g of this isotope to decay to 0.25 g?
MASS
8
4
2
1
.5
.25
4
½ LIFE
0
1
2
3
4
5
Page
TIME
0
164
328
492
656
820
Name: _________________________________
4. How many days does it take for 16 g of palladium-103 to decay to 1.0 g?
The half-life of palladium-103 is 17 days.
½ LIFE
0
1
2
3
4
TIME
0
17
34
68
68
MASS
16
8
4
2
1
5. In 5.49 seconds, 1.20 g of argon-35 decay to leave only 0.15 g. What is
the half-life of argon-35?
½ LIFE
TIME
0
1.83
3.66
5.49
0
1
2
3
MASS
1.2
.6
.3
.15
½ LIFE
0
1
2
3
4
5
MASS
1.0
.5
.25
.125
.0625
.03125
Page
TIME
0
30.2
60.4
90.6
120.8
151
5
6. The half-life of Cs-137 is 30.2 years. If the initial mass of the sample is
1.00kg, how much will remain after 151 years?
Name: _________________________________
Half life = decay time ÷ # of half lives
7. Carbon-14
has a half-life of
5730 years.
Consider a
sample of fossilized wood that when alive would have contained 24g of C-14. It
now contains 1.5g. How old is the sample?
TIME
0
5730
11460
17190
22920
½ LIFE
0
1
2
3
4
MASS
24
12
6
3
1.5
8. A 64g sample of Germanium-66 is left undisturbed for 12.5 hours. At the
end of that period, only 2.0g remain. What is the half-life of this material?
TIME
0
2.5
5.0
7.5
10.0
12.5
½ LIFE
0
1
2
3
4
5
MASS
64
32
16
8
4
2
Page
6
Half life = decay time ÷ # of half lives