Adapted by Nelson Nuñez-Rodriguez
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By David W. Ball
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| QUESTION | ANSWER |
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1. Given that many elements are metals, suggest why it would be unsafe to have radioactive materials in contact with acids. |
1. Acids can dissolve many metals; a spilled acid can lead to contamination. |
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3. Uranium can be separated from its daughter isotope thorium by dissolving a sample in acid and adding sodium iodide, which precipitates thorium(III) iodide: Th3+(aq) + 3I−(aq) → ThI3(s) If 0.567 g of Th3+ were dissolved in solution, how many milliliters of 0.500 M NaI(aq) would have to be added to precipitate all the thorium? |
3. 14.7 mL |
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5. Radioactive strontium is dangerous because it can chemically replace calcium in the human body. The bones are particularly susceptible to radiation damage. Write the nuclear equation for the beta emission of strontium-90. |
5. |
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7. A common uranium compound is uranyl nitrate hexahydrate [UO2(NO3)2 ⋅ 6H2O]. What is the formula mass of this compound? |
7. 502.15 g/mol |
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9. A banana contains 600 mg of potassium, 0.0117% of which is radioactive potassium-40. If 1 g of potassium-40 has an activity of 2.626 × 105 Bq, what is the activity of a banana? |
9. about 18 Bq |
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11. Uranium hexafluoride (UF6) reacts with water to make uranyl fluoride (UO2F2) and HF. Balance the following reaction: UF6 + H2O → UO2F2 + HF |
11. UF6 + 2H2O → UO2F2 + 4HF |
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13. If the half-life of hydrogen-3 is 12.3 y, how much time does it take for 99.0% of a sample of hydrogen-3 to decay? |
13. 81.7 y |
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15. Although bismuth is generally considered stable, its only natural isotope, bismuth-209, is estimated to have a half-life of 1.9 × 1019 y. If the universe is estimated to have a lifetime of 1.38 × 1010 y, what percentage of bismuth-209 has decayed over the lifetime of the universe? (Hint: Be prepared to use a lot of decimal places.) |
15. about 0.000000005% |
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17. Refer to Table 6.3 "Average Annual Radiation Exposure (Approximate)" and separate the sources of radioactive exposure into voluntary and involuntary sources. What percentage of radioactive exposure is involuntary? |
17. Radioactive atoms in the body, terrestrial sources, and cosmic sources are truly involuntary, which is about 27% of the total. Radon exposure, medical sources, consumer products, and even nuclear energy sources can be avoided. |