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## Half Life Practice

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**You have 5g of sodium 25. How much would you have after 3**half lives? Step 1: 2512.56.25 6.25g remain**C14 has a half life of 5730 years. If you had 88g, how much**C14 would remain after 5 half lives? Step 1: 884422115.52.75g**Actinium 226 has a half life of 28 hours. 100 g of actinium**226 degrades over 56 hours. How much will be left? Step 1: 56/28=2 Step 2: 100g50g25g 25g**After 11,200 years, a sample of radium-226 has decayed. It**has a half-life of 1600 years. The sample was originally 162 grams. How much is left? Step 1: 11,200/1600=7 Step 2: 1628140.520.2510.1255.0625 2.53125 2.53125g**The half life of isotope X is 2 years. How long would it**take for 4g to decay to .5g? Step 1: 421.5 (3 Half lives have passed) Step 2: 3X2years=6 years**Carbon has a half life of 5730 years. How long would it take**100g to decay to 25 grams? Step 1: 1005025 (2 half lives have passed) Step 2: 5730 years X 2=11460 Years**A sample initially contains 60g of thorium 234. After 48**days only 7.5 grams remain. How long is one half life? Step 1: 6030157.5 (3 half lives have passed) Step2: 48/3=16 16 days**We start with 500g of isotope X. In 10,000 years we end with**7.8g. How ling is one half life for isotope X? Step 1: 50025012562.531.2515.67.8 (6 half lives have passed) Step 2: 10,000/6 = 1666.66 One half life is 1666.66 years