Page 361 - Teacher Preview Copy
P. 361
. r Chemistry
Topic 12: Nuclea
20. Half-life problems: Determining original mass
1. After 4 half-life periods, 1.5 mg of a radioactive isotope remained. What was the mass of the
original sample of the isotope?
1) 6.0 mg 2) 3.0 mg 3) 12 mg 4) 24 mg
2. If 10.0 grams of P-32 remains after 3 half-life periods, what was the original mass of P-32?
1) 60.0 g 2) 30.0 g 3) 20.0 g 4) 3.33 g
198
3. What was the original mass of Au if only 4 grams of the isotope remained after about 8 days?
3) 8 g
4) 32 g
2) 4 g
1) 2 g
4. A sample of iodine-131 decays to 1.0 g in 40 days. What was the mass of the original sample?
Teacher Preview Copy
1) 8.0 g 2) 16 g 3) 32 g 4) 4.0 g
99
6
5. A sample of Tc decays to 0.5 grams in 1.49 x 10 years. What was the mass of the original
sample? 2) 32 g 3) 128 g 4) 8 g
1) 64 g
21. Half-life: Determining fraction remaining
1. What fraction of a radioactive substance will remain after 3 half-life periods? 1
1
1
1
1) /2 2) /3 3) /4 4) /8
2. What fraction of the radioactive waste Strontium-90 will remain unchanged after 5 half-life
periods of decaying?
1) ½ Teacher Preview Copy 1
1
1
1
1) /32 2) /16 3) /8 4) /5
3. A radioactive element has a half-life of 2 days. Which fraction represents the amount of an
original sample of this element remaining after 6 days? 3) / 3 1
1
1
1
2) /2
1) / 6
4) /8
4. If the half-life of a radioactive element is 2.5 years, what fraction of this element will remain
unchanged after 15 years?
1) /32 2) /2 3) /16 4) /64
1
1
1
1
5. According to Reference Table N, what fraction of Rn-222 will remain unchanged after 3.82 days?
1
1
1
1
1) /8 2) / 4 3) /2 4) /3
6. After 55 days of decaying, what fraction of a sample of Fr-220 will remain unchanged?
1
1
2) ¼ 3) /8 4) /16
7. Approximately what fraction of an original Co sample remains unchanged after 21 years?
60
1
1
1
1
1) / 2 2) / 4 3) /8 4) / 16
8. What fraction of a 10 gram sample of Cesium – 137 will remain unchanged after 90.7 years?
1) /9 2) /2 3) /8 4) /3
1
1
1
1
9. After 1.42 x 10 years, what fraction of a 6 gram sample of U-235 will remain unchanged?
9
1
1
1) /2 2) /4 3) /6 4) /8
1
1
10. Approximately what fraction of Tc will remain unchanged after 8.52 x 10 years?
5
99
1) /2 2) /8 3) /16 4) /4
1
1
1
1
Copyright©2010 E3 Scholastic Publishing. All Rights Reserved. SurvivingChem.com 351
Topic 12: Nuclea
20. Half-life problems: Determining original mass
1. After 4 half-life periods, 1.5 mg of a radioactive isotope remained. What was the mass of the
original sample of the isotope?
1) 6.0 mg 2) 3.0 mg 3) 12 mg 4) 24 mg
2. If 10.0 grams of P-32 remains after 3 half-life periods, what was the original mass of P-32?
1) 60.0 g 2) 30.0 g 3) 20.0 g 4) 3.33 g
198
3. What was the original mass of Au if only 4 grams of the isotope remained after about 8 days?
3) 8 g
4) 32 g
2) 4 g
1) 2 g
4. A sample of iodine-131 decays to 1.0 g in 40 days. What was the mass of the original sample?
Teacher Preview Copy
1) 8.0 g 2) 16 g 3) 32 g 4) 4.0 g
99
6
5. A sample of Tc decays to 0.5 grams in 1.49 x 10 years. What was the mass of the original
sample? 2) 32 g 3) 128 g 4) 8 g
1) 64 g
21. Half-life: Determining fraction remaining
1. What fraction of a radioactive substance will remain after 3 half-life periods? 1
1
1
1
1) /2 2) /3 3) /4 4) /8
2. What fraction of the radioactive waste Strontium-90 will remain unchanged after 5 half-life
periods of decaying?
1) ½ Teacher Preview Copy 1
1
1
1
1) /32 2) /16 3) /8 4) /5
3. A radioactive element has a half-life of 2 days. Which fraction represents the amount of an
original sample of this element remaining after 6 days? 3) / 3 1
1
1
1
2) /2
1) / 6
4) /8
4. If the half-life of a radioactive element is 2.5 years, what fraction of this element will remain
unchanged after 15 years?
1) /32 2) /2 3) /16 4) /64
1
1
1
1
5. According to Reference Table N, what fraction of Rn-222 will remain unchanged after 3.82 days?
1
1
1
1
1) /8 2) / 4 3) /2 4) /3
6. After 55 days of decaying, what fraction of a sample of Fr-220 will remain unchanged?
1
1
2) ¼ 3) /8 4) /16
7. Approximately what fraction of an original Co sample remains unchanged after 21 years?
60
1
1
1
1
1) / 2 2) / 4 3) /8 4) / 16
8. What fraction of a 10 gram sample of Cesium – 137 will remain unchanged after 90.7 years?
1) /9 2) /2 3) /8 4) /3
1
1
1
1
9. After 1.42 x 10 years, what fraction of a 6 gram sample of U-235 will remain unchanged?
9
1
1
1) /2 2) /4 3) /6 4) /8
1
1
10. Approximately what fraction of Tc will remain unchanged after 8.52 x 10 years?
5
99
1) /2 2) /8 3) /16 4) /4
1
1
1
1
Copyright©2010 E3 Scholastic Publishing. All Rights Reserved. SurvivingChem.com 351
