NAME ______________________________________________________ DATE _________________
Half-life Practice
1. What is half-life? _THE AMOUNT OF TIME REQUIRED FOR HALF OF THE ORIGINAL SAMPLE TO
DECAY_
2. If we start with 400 atoms of a radioactive substance, how many would we have after:
a. one half-life?
_200__
c. three half-lives?
_50_
b. two half-lives?
__100_
d. four half-lives?
_25_
3. If we start with 48 atoms of a radioactive substance, how many would remain after:
a. one half-life?
_24_
c. after three half-lives?
__6_
b. two half-lives?
_12_
d. after four half-lives?
_3_
Using the graph to the right, answer
the following questions.
4.What is the half-life of each element?
A.1.25 x 109 years
B. 4.5 x 109 years
C. 13 x 109 years
5.Which element has the shortest half-life?
A
Use the graph to answer the following questions.
6. How many atoms are in the original sample size of this
radioisotope? 80
7. How long is the half-life? 2 DAYS
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Use the table on the right to answer the
following questions.
8. How long is a half-life for carbon-14?
5730 YEARS
9. If only 25% of the carbon-14 remains,
how old is the material containing the
carbon-14?
10,740
The table below shows the radioactive decay of a 600 g sample of Iodine-125.
% of Parent Isotope
Fraction of Parent
Time
HalfMass (g) of Parent
Remaining
Isotope
Remaining
Isotope
(days)
Lives
0
0
100%
1/1
600
60
1
50%
1/2
300
120
2
25%
1/4
150
180
3
12.5%
1/8
75
240
4
6.25%
1/16
37.5
300
5
3.125%
1/32
18.75
360
6
1.56%
1/64
9.4
10. What percent of iodine is left if 5 half-lives have passed?
0
300
450
325
562.5
581.25
590.6
____3.25 %___
11. What is the half-life time of Iodine-125?
__ 60 DAYS _
12. What fraction of the Iodine-125 remains after 300 days have passed?
__ 1/32 _
13. How many half-lives have occurred for there to be 75 grams remaining?
__ 3 __
This study source was downloaded by 100000855867892 from CourseHero.com on 11-07-2022 08:44:28 GMT -06:00
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Mass (g) of
Daughter Isotope