Half-Life Questions

Titanium-51 decays with a half life of 6 minutes. What fraction of titanium would remain after one hour?

1/1024

Iodine-131 has a half life of 8 days. What fraction of the original sample would remain at the end of 32 days?

1/16

The half life of Uranium-238 is 4.5 billion years and the age of earth is 4.5 X 109 years. What fraction of Uranium-238 that was present when Earth was formed still remains?

1/2

Fluorine-21 has a half life of approximately 5 seconds. What fraction of the original nuclei would remain after 1 minute?

1/4096

Chromium-48 decays. After 6 half-lives, what fraction of the original nuclei would remain?

1/64

The half life of iodine-125 is 60 days. What fraction of iodine-125 nuclides would be left after 360 days?

1/64

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?

30 minutes.

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?

32kg

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 days: 127.5g 1 year: 0.062g 168 days: 32kg

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?

x = 64g