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Practice Problems for study packet:
| 25.1 | 1. atomic number increases by one: the mass number remains the
same 2. Atomic number decreases by two: the mass number decreases by four. 3. a. 28 p ,3 6 n b. 53 p , 83 n c. 79 p, 116 n 4. a. 14 N , b. 237 Np c. 0 e 7 93 -1 |
| 25.2 | 1. a. 208 Fr → 4He
+ 204 At 87 2 85 b. 7Be + 0e → 7Li 4 -1 3 2. a. 3H b. 92 Kr c. 30P d. 144Ce e. 239Pu 1 36 15 58 94 3. It takes five 1/2-lives. or 820 s. 8.0g → 4.0g → 2.0g → 1.0g → 0.50g → 0.25g 4. 16.0g → 8.0g → 4.0g → 2.0g → 1.0g → 0.50g → 0.25g 4 1/2-lives = 4 x 17days = 68 days 5. 51 min. = 10 half-lives. The mass decreases by a factor of more than 1000. 5.1 min. (1/2)10 = 1/1024 6. The mass decreases by a factor of 1/8 or three half-lives. The half-life is 5.49/3 = 183 s |
| 25.3 | 1. a. 2 ([1 = 235] - {[90 + 144] = 2) 2. 2.0 x 107 kcal ÷ 8.0 kcal/g = 2.5 x 106g 3. 4 He 2 |
| 25.4 | 1. Radioisotopes replace non-radioactive isotopes in the
structure of a compound without changing its chemical properties.
Tracing the pathways of radioactive isotopes allow scientists to study
reaction mechanisms and reaction rates. 2. Teletherapy is the use of gamma radiation to destroy cancerous tissue. |