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Honors Chem

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Directions: The following questions involve more practice with radioactive decay half-life. Complete the problems to the best of your ability. This assignment is due by next WEDNESDAY, November 16th. 1. 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? a. Calculate how many half-lives have passed during the decay of the 100.0 g sample. 100 grams/2 50 grams/2 25grams…2 half lives have passed b. Solve for the half-life. 11,460year/2 half lives = 5,730 years half-life of carbon – 14 2. What is the half-life of a 100.0 g sample of nitrogen-16 that decays to 12.5 g of nitrogen-16 in 21.6 s? 100g50g25g12.5g…3 half lives have passed 21.6s/3 half …show more content…

150days/30days = 5 half lives have passed 200mg/2 100mg/2 50mg/2 25mg/2 12.5mg/2 6.25mg of polonium – 210 remain 16. A 1000 gram sample of Titanium-50 decays to 62.5 grams in 2000 years. What is the half-life of Titanium-50? 1000g/2 500g/2 250g/2 125g/2 62.5g … 4 half lives have passed 2000years/4 half lives = 500years half-life of Titanium – 50 17. The half-life of Potassium-44 is 10 days. If after 50 days you end up with 15 grams of Potassium-44, how many grams did you start with? 50days/10days = 5 half lives have passed WORKING BACKWARDS in time… 15g x 2 30g x 2 60g x 2 120g x 2 240g x 2 480g …amount of potassium – 44 you started with 18. The half life of Carbon-14 is 5730 years. A scientist finds a 17190 year old fossil of a bumble bee. A live bumble bee of this kind has 600 million atoms of Carbon-14. How many atoms of Carbon-14 are in this fossil? 17,190years/5,730years = 3 half lives have passed 600 million atoms/2 300 million atoms/2 150 million atoms/2 75 million atoms of carbon – 14 are found in this fossil 19. The half life of Polonium-210 is 140 days. How many milligrams of polonium-210 remain after 420 days if you start with 20 milligrams? 420days/140days = 3 half lives 20mg/2 10mg/2 5mg/2 2.5 mg of polonium – 210 remain after 420 days 20. A 600 gram sample of Nitrogen-18 decays to 75 grams in 750 seconds. What is the half-life of

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