Honors PS Chemistry Chapter 18 Name_______________________Period____ Half-life Practice Worksheet Complete the following problems. Please show your work. You may use a table to guide your thought process. Table: Time Half-Life # atoms remaining (or grams) 1. How many days does it take for 16 g of palladium-103 to decay to 8.0 g? The half-life of palladium-103 is 17 days. 2. If the half-life of iodine-131 is 8.10 days, how long will it take a 50.00 g sample to decay to 6.25 g? 3. What is the half-life of a 100.0 g sample of nitrogen16 that decays to 12.5 g of nitrogen-16 in 21.6 s? 4. If 100.0 g of carbon-14 decays until only 25.0 g of carbon is left after 11 460 y, what is the half-life of carbon-14? 5. A 208 g sample of sodium-24 decays to 13.0 g of sodium-24 within 60.0 h. What is the half-life of this radioactive isotope? % of atoms remaining 6. After 42 days a 2.0 g sample of phosphorus-32 contains only 0.25 g of the isotope. What is the halflife of phosphorus-32? 7. In 5.49 seconds, 1.20 g of argon-35 decay to leave only 0.15 g. What is the half-life of argon-35? 8. Potassium-42 has a half-life of 12.4 hours. How much of an 848 g sample of potassium-42 will be left after 62.0 hours? 9. Sodium-24 has a half-life of 15 hours. How much sodium-24 will remain in an 18.0 g sample after 60 hours? 10. Carbon-14 has a half-life of 5730 years. How “old” would a real fossil be after 4 carbon-14 half-lives? Complete the following problems. Please show your work. Use the exponential decay function as shown below. t = elapsed time ( )t/T T = half-life 11. The half-life of is 32 minutes. How much of a 16.0 gram sample of this isotope will remain at the end of 3.0 hours? 13. The half-life of is 9.0 x 106 years. How much of a 1.0-g sample of this isotope will remain at the end of 40.0 million years? 12. The isotope strontium-90 is produced during the testing of nuclear weapons. If 100.0 mg of strontium-90 was released in the atmosphere in 1960, how much of the radioisotope remains 85 years later? The half-life of strontium-90 is 29 years. 14. The radioisotope technetium-99 is often used as a radiotracer to detect disorders of the body. It has a half-life of 6.01 hours. If a patient received a 25.0mg dose of this isotope during a medical procedure, how much would remain 48.0 hours after the does was given? Multiple Choice: Choose the letter of the best answer, and write it in the blank. _____15. If the half-life of Radon-222 is 3.8 days, how much of a 100.0 mg sample will remain after 3.8 days? a.) 100.0 mg b.) 50.00 mg c.) 25.00 mg d.) 12.50 mg e.) 6.250 mg f.) None of the preceding _____16. If the half-life of Radon-222 is 3.8 days, how much of a 100.0 mg sample will remain after 7.6 days? a.) 100.0 mg b.) 50.00 mg c.) 25.00 mg d.) 12.50 mg e.) 6.250 mg f.) None of the preceding _____17. If the half-life of Radon-222 is 3.8 days, how much of a 100.0 mg sample will remain after 15.2 days? a.) 100.0 mg b.) 50.00 mg c.) 25.00 mg d.) 12.50 mg e.) 6.250 mg f.) None of the preceding _____18. If the half-life of Radon-222 is 3.8 days, how much of a 100.0 mg sample will remain after 22.8 days? a.) 100.0 mg b.) 50.00 mg c.) 25.00 mg d.) 12.50 mg e.) 6.250 mg f.) None of the preceding _____19. If the half-life of Phosphorus-32 is 14.28 days, how much of a 38.2 g sample will remain after 2 half-lives? a.) 38.2 g b.) 9.55 g c.) 4.78 g d.) 1.19 g e.) 0.597 g f.) None of the preceding _____20. If the half-life of Phosphorus-32 is 14.28 days, how much of a 38.2 g sample will remain after 42.84 days? a.) 38.2 g b.) 9.55 g c.) 4.78 g d.) 1.19 g e.) 0.597 g f.) None of the preceding _____21. If the half-life of Phosphorus-32 is 14.28 days, how much of a 38.2 g sample will remain after 4 half-lives? a.) 38.2 g b.) 9.55 g c.) 4.78 g d.) 1.19 g e.) 0.597 g f.) None of the preceding _____22. If the half-life of Phosphorus-32 is 14.28 days, how much of a 38.2 g sample will remain after 85.68 days? a.) 38.2 g b.) 9.55 g c.) 4.78 g d.) 1.19 g e.) 0.597 g f.) None of the preceding

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