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Topic 12: Nuclear Chemistry
22. Half-life problems: Using fraction remaining in half-life problems
th
1
1. In how many half-life periods would a sample of a radioisotope decays to /8 its original mass?
4) 4
3) 3
1) 1
2) 2
1 th
2. What is the total number of half-life periods it will take for any sample of Co-60 to decay to /16
of its original mass?
1) 1 2) 2 3) 3 4) 4
3. After 60 years, ½ of an original sample of a radioactive substance remained unchanged. What is
the half-life of this radioactive substance? 3) 30 years 4) 60 years
2) 20 years
1) 10 years
1 th
4. A sample of a radioisotope Cr-51 decays to /8 in 84 days, what is the half-life of Cr-51?
1) 14 days
3) 56 days
4) 84 days
2) 28 days
1 th
Teacher Preview Copy
5. What is the half of sodium-22 if, after 13 years, only /32 of an original sample of sodium-22 will
remain unchanged?
1) 13.0 years 2) 26.0 years 3) 2.6 years 4) 5.2 years
6. If the half-life of a radioactive O-15 is 122 seconds. How long will it take for a sample of this
th
1
isotope to decay to /4 its original mass?
1) 61 s 2) 122 s 3) 244 s 4) 488 s
59
7. The half life of the isotope Fe is 44.5 days. In approximately how many days will it take for a
59
1
th
10 gram sample of Fe to decay to /8 its original mass.
1) 133.5 days 2) 89.0 days 3) 44.5 days 4) 22.25 days
8. A radioisotope has a half-life of 16 years. In how many years would a given sample of this isotope
1
th
decays leaving only /32 of this isotope remaining?
3) 2 years
2) 80 years
4) 512 years
1) 8 years Teacher Preview Copy
23. Half-Life problems: Determining correct radioisotope
1. According to Reference Table N, a 10 gram sample of which radioisotope will decay to the greatest
extent in 28 days?
1) P 2) Kr 3) 220 Fr 4) I
85
131
32
2. Which radioisotope will decay the most over a period of 100 days? 4) Rn
198
222
131
32
Au
3)
2) I
1) P
3. Which 20 gram sample of a radioisotope will have the highest percentage remaining after 5000 years
of decaying?
1) Pu-239 2) Th-232 3) U-238 4) Tc-99
4. A sample of which radioisotope will decay the least over a period of 100 years?
1) 5g of Co-60 2) 5 g of H-3 3) 5 g of Kr-85 4) 5 g of Sr-90
5. Which radioisotope sample will have the greatest amount remaining after 10 years?
1) 2.0 g of Au-198 2) 2.0 g of K-42 3) 4.0 g of P-32 4) 4.0 g of Co-60
th
6. According to Reference Table N, which radioisotope will retain only 1/8 its original mass after
approximately after 43 days?
1) Phosphorous-32 2) Radon-222 3) Gold-198 4) Iron-53
7. Which of the following isotopes will have only ¼ of its original atoms remaining unchanged after
approximately 14.4 seconds?
16
220
37
19
1) Ne 2) N 3) K 4) Fr
352 Copyright © 2010 E3 Scholastic Publishing. All Rights Reserved. Survivingchem.com
Topic 12: Nuclear Chemistry
22. Half-life problems: Using fraction remaining in half-life problems
th
1
1. In how many half-life periods would a sample of a radioisotope decays to /8 its original mass?
4) 4
3) 3
1) 1
2) 2
1 th
2. What is the total number of half-life periods it will take for any sample of Co-60 to decay to /16
of its original mass?
1) 1 2) 2 3) 3 4) 4
3. After 60 years, ½ of an original sample of a radioactive substance remained unchanged. What is
the half-life of this radioactive substance? 3) 30 years 4) 60 years
2) 20 years
1) 10 years
1 th
4. A sample of a radioisotope Cr-51 decays to /8 in 84 days, what is the half-life of Cr-51?
1) 14 days
3) 56 days
4) 84 days
2) 28 days
1 th
Teacher Preview Copy
5. What is the half of sodium-22 if, after 13 years, only /32 of an original sample of sodium-22 will
remain unchanged?
1) 13.0 years 2) 26.0 years 3) 2.6 years 4) 5.2 years
6. If the half-life of a radioactive O-15 is 122 seconds. How long will it take for a sample of this
th
1
isotope to decay to /4 its original mass?
1) 61 s 2) 122 s 3) 244 s 4) 488 s
59
7. The half life of the isotope Fe is 44.5 days. In approximately how many days will it take for a
59
1
th
10 gram sample of Fe to decay to /8 its original mass.
1) 133.5 days 2) 89.0 days 3) 44.5 days 4) 22.25 days
8. A radioisotope has a half-life of 16 years. In how many years would a given sample of this isotope
1
th
decays leaving only /32 of this isotope remaining?
3) 2 years
2) 80 years
4) 512 years
1) 8 years Teacher Preview Copy
23. Half-Life problems: Determining correct radioisotope
1. According to Reference Table N, a 10 gram sample of which radioisotope will decay to the greatest
extent in 28 days?
1) P 2) Kr 3) 220 Fr 4) I
85
131
32
2. Which radioisotope will decay the most over a period of 100 days? 4) Rn
198
222
131
32
Au
3)
2) I
1) P
3. Which 20 gram sample of a radioisotope will have the highest percentage remaining after 5000 years
of decaying?
1) Pu-239 2) Th-232 3) U-238 4) Tc-99
4. A sample of which radioisotope will decay the least over a period of 100 years?
1) 5g of Co-60 2) 5 g of H-3 3) 5 g of Kr-85 4) 5 g of Sr-90
5. Which radioisotope sample will have the greatest amount remaining after 10 years?
1) 2.0 g of Au-198 2) 2.0 g of K-42 3) 4.0 g of P-32 4) 4.0 g of Co-60
th
6. According to Reference Table N, which radioisotope will retain only 1/8 its original mass after
approximately after 43 days?
1) Phosphorous-32 2) Radon-222 3) Gold-198 4) Iron-53
7. Which of the following isotopes will have only ¼ of its original atoms remaining unchanged after
approximately 14.4 seconds?
16
220
37
19
1) Ne 2) N 3) K 4) Fr
352 Copyright © 2010 E3 Scholastic Publishing. All Rights Reserved. Survivingchem.com
