University:
High School
Course:
High School Mathematics
Academic year:

2022
Views:

396

Pages:

2
Author:

nadelnnl7v

Name: _________ANSWER KEY_________________ Date: _____________________________ Period: _________ Half Life Worksheet #2 1) Fluorine-21 has a half life of approximately 5 seconds. What fraction of the original nuclei would remain after 1 minute? 60 seconds/ 5 seconds = 12 half lives 1  ½  ¼  1/8  1/16  1/32  1/64  1/128  1/256  1/512  1/1024  1/2048  1/4096 will remain 2) Iodine-131 has a half life of 8 days. What fraction of the original sample would remain at the end of 32 days? 32 days /8 days = 4 half lives 1  ½  ¼  1/8  1/16 will remain 3) The half-life of chromium-51 is 28 days. If the sample contained 510 grams, how much chromium would remain after 56 days? How much would remain after 1 year? How much was present 168 days ago? 56/28 = 2 half lives 510  255  130 grams 365/28 = 13 half lives 510  255  127.5  63.75  31.875  15.9375  7.96875  3.9843  1.9922  0.996  0.498  0.249  0.124  0.062 grams 168/28 = 6 half lives 510  255  127.5  63.75  31.875  15.9375  7.97 grams 4) If 20.0 g of a radioactive isotope are present at 1:00 PM and 5.0 g remain at 2:00 PM, what is the half life of the isotope? 20  10  5 2 half lives 1pm – 2pm = 1 hour/2 = 30. minutes 5) The half life of Uranium-238 is 4.5 billion years and the age of earth is 4.5 X 10 9 years. What fraction of Uranium-238 that was present when Earth was formed still remains? 4.5 billion / 4.5 billion = 1 half life has happened ½ still remains 6) Chromium-48 decays. After 6 half-lives, what fraction of the original nuclei would remain? 1  ½  ¼  1/8  1/16  1/32  1/64 7) The half life of iodine-125 is 60 days. What fraction of iodine-125 nuclides would be left after 360 days? 360/60 = 6 half lives 1  ½  ¼  1/8  1/16  1/32  1/64 8) Titanium-51 decays with a half life of 6 minutes. What fraction of titanium would remain after one hour? 60 minutes/6 min = 10 half lives 1  ½  ¼  1/8  1/16  1/32  1/64  1/128  1/256  1/512  1/1024 9) A medical institution requests 1 g of bismuth-214, which has a half life of 20 min. How many grams of bismuth-214 must be prepared if the shipping time is 2 h? 120 min/20 min = 6 half lives 1  2  4  8  16  32  64 grams prepared 10)The half life of radium 226 is 1602 years. If you have 500 grams of radium today how many grams would have been present 9612 years ago? 9612 / 1602 = 6 half lives 500  1000  2000  4000  8000  16000  32000 grams