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WorksheetsHalf-Life Practice Problems
Total questions: 20
Worksheet time: 3hrs 33mins
Name
Class
Date
1.
What is Half-life?
a)
The amount of time it takes for some of the nuclei in a sample of the isotope to decay
b)
The amount of time it takes for half the electrons in a sample of the isotope to decay
c)
The amount of time it takes for half the nuclei in a sample of the isotope to decay
d)
the amount of time it takes to double the nuclei in a sample of the isotope to decay
2.
The half-life of Zn-71 is 2.4 minutes. If one had 100.0 g at the beginning, how many grams would be left after 7.2 minutes has elapsed?
a)
100.0g
b)
50.0g
c)
12.5g
d)
8.5g
3.
Fermium-253 has a half-life of 0.334 seconds. A radioactive sample is considered to be completely decayed after 10 half-lives. How much time will elapse for this sample to be considered gone?
a)
0.334 seconds
b)
3.34 seconds
c)
1.77 seconds
d)
13.4 seconds
4.
After the third half-life, how much of the sample is left?
a)
1/2
b)
1/3
c)
1/16
d)
1/8
5.
The half life of iodine-131 is 8.040 days. What percentage of an iodine-131 sample will remain after 40.20 days?
a)
312.5%
b)
31.25%
c)
.3125%
d)
3.125%
6.
Barium-122 has a half-life of 2 minutes. A fresh sample weighing 80 g was obtained. If it takes 10 minutes to set up an experiment using barium-122, how much barium-122 will be left when the experiment begins?
a)
0.25g
b)
2.5g
c)
25g
d)
80g
7.
If 10 mg of iodine 131 is given to a patient, how much is left after 24 days? The half-life of iodine-131 is 8 days.
a)
1.25mg
b)
1.25g
c)
10g
d)
10mg
8.
The half-life of strontium-90 is 25 years. How much strontium-90 will remain after 100 years if the initial amount is 4.0 g?
a)
3.0g
b)
0.25mg
c)
0.3g
d)
0.25g
9.
If the half-life of uranium-232 is 70 years, how many half-lives will it take for 10 g of it to be reduced to 1.25 g?
a)
1 half-life
b)
2 half-lives
c)
3 half-lives
d)
4 half-lives
10.
What is the half-life of iodine-131?
a)
32 days
b)
8 days
c)
16 days
d)
24 days
11.
What is the Half life of this isotope?
a)
5 seconds
b)
10 seconds
c)
15 seconds
d)
20 seconds
12.
What is the Half Life of this isotope?
a)
3 days
b)
5 days
c)
8 days
d)
10 days
13.
Which diagram best represents the percentage of this radioactive isotope sample that will remain after 2 half-lives?
a)
b)
c)
d)
14.
You have 100 grams of radioactive C-14. The half life of C-14 is 5730 years.
How many grams are left after 1 half life?
How many grams are left after 1 half life?
a)
100 grams
b)
25 grams
c)
2 grams
d)
50 grams
15.
After 22,800 years, approximately what percentage of the original carbon-14 remains?
a)
15%
b)
12.5%
c)
6.25%
d)
3.125%
16.
If one-fourth of the carbon-14 is remaining then how many half-lives have passed?
a)
1
b)
2
c)
3
d)
4
17.
When nuclei decay, massive amounts of __________ is released.
a)
energy
b)
jello
c)
protons
d)
neutrons
18.
A radioisotope of silver has half life of 10 minutes. What fraction of the original mass would remain after one hour?
a)
1/64
b)
1/2
c)
1/4
d)
1/8
19.
Selenium-83 has a half life of 25 minutes. How many minutes would it take for a 20 milligram sample to decay and only have 1.25 milligrams of it remaining?
a)
25 minutes
b)
50 minutes
c)
75 minutes
d)
100 minutes
20.
Geologist use the time it takes for a radioactive isotope to decay to half its original mass called a___________.
a)
radioactive decay
b)
isotope
c)
half-life
d)
carbon dating
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