## Chemistry and Chemical Reactivity (9th Edition)

Published by Cengage Learning

# Chapter 25 Nuclear Chemistry - Study Questions - Page 1007b: 29

#### Answer

$0.781\,\mu g$

#### Work Step by Step

Time elapsed=63.5 hours=$\frac{63.5\,hours}{12.7\,hours}$ half-lives= 5 half-lives. The amount of Cu-64 has decreased to $(\frac{1}{2}\times\frac{1}{2}\times\frac{1}{2}\times\frac{1}{2}\times\frac{1}{2})$ of the original amount. The amount of Cu-64 remaining$=25.0\,\mu g\times(\frac{1}{2})^{5}=25.0\,\mu g\times\frac{1}{32}=0.781\,\mu g$

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