Chemistry: An Introduction to General, Organic, and Biological Chemistry (12th Edition)

Published by Prentice Hall
ISBN 10: 0321908449
ISBN 13: 978-0-32190-844-5

Chapter 5 - Section 5.4 - Half-Life of a Radioisotope - Questions and Problems - Page 152: 5.33b

Answer

There are necessary 200 days to drop the radiation level of strontium-85 to one-eighth of its original level.

Work Step by Step

1. After one half-life, the level of strontium-85 is dropped to one-half of its original level. $[Strontium-85] = \frac{1}{2}[Strontium-85]_{initial}$ 2. After the second half-life, the level of strontium-85 is dropped to one-fourth of its original level. $[Strontium-85] = \frac{1}{2}(\frac{1}{2}[Strontium-85]_{initial}) = \frac{1}{4}[Strontium-85]_{initial}$ 3. After the third half-life, the level of strontium-85 is dropped to one-eighth of its original level. $[Strontium-85] = \frac{1}{2}(\frac{1}{4}[Strontium-85]_{initial}) = \frac{1}{8}[Strontium-85]_{initial}$ 4. Since we have determined the number of half-lives (3), we can calculate how long will it take. $3 half-lives \times \frac{65 days}{1half-life} = 200 days $
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.