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Worksheets13-02: Half-life
Total questions: 15
Worksheet time: 8mins
Based on Table N, uranium-238 and uranium-235 have different
decay modes
half-lives
numbers of protons
number of electrons
What is the mass of an original 5.60-gram sample of iron-53 that remains unchanged after 25.53 minutes?
0.35 g
0.70 g
1.40 g
2.80 g
A radioactive isotope has a half-life of 2.5 years. Which fraction of the original mass remains unchanged after 10 years?
1/2
1/4
1/8
1/16
Compared to the half-life and decay mode of the nuclide 90Sr, the nuclide 226Ra has
a longer half-life and the same decay mode
a longer half-life and a different decay mode
a shorter half-life and the same decay mode
a shorter half-life and a different decay mode
After decaying for 48 hours, 1/16 of the original mass of a radioisotope sample remains unchanged. What is the half-life of this radioisotope?
3.0 h
9.6 h
12 h
24 h
What fraction of a Sr-90 sample remains unchanged after 87.3 years?
1/2
1/3
1/4
1/8
What is the half-life of a radioisotope if 25.0 grams of an original 200-gram sample of the isotope remains unchanged after 11.46 days?
2.87 d
3.82 d
11.46 d
34.38 d
An original sample of the radioisotope fluorine-21 had a mass of 80.0 milligrams. Only 20.0 milligrams of this original sample remain unchanged after 8.32 seconds. What is the half-life of fluorine-21?
1.04 s
2.08 s
4.16 s
8.32 s
An original sample of K-40 has a mass of 25.00 grams. After 3.9 x 10^9 years, 3.125 grams of the original sample remains unchanged. What is the half-life of K-40?
1.3 x 109 y
2.6 x 109 y
3.9 x 109 y
1.2 x 1010 y
As the temperature of a sample of a radioactive element decreases, the half-life of the element will
decrease
increase
remain the same
The half-life of I-131 is 8.021 days. What fraction of a sample of I-131 remains after 24.063 days?
1/2
1/4
1/8
1/16
Based on Reference Table N, which radioactive isotope is best represented by the graph showing a decay curve in the image?
32P
131I
198Au
222Rn
What fraction of an original 20.00-gram sample of nitrogen-16 remains unchanged after 35.65 seconds?
1/5
1/8
1/16
1/32
What is the half-life of sodium-25 if 1.00 gram of a 16.00-gram sample of sodium-25 remains unchanged after 237 seconds?
47.4 s
59.3 s
79.0 s
118 s
What is the half-life and decay mode of Rn-222?
1.91 days and alpha decay
1.91 days and beta decay
3.823 days and alpha decay
3.823 days and beta decay
