# Question #5563a

Mar 26, 2014

By the time you begin the experiment, 1.04 g of barium-122 will remain.

The first step is to determine the number of half-lives that have elapsed.

Number of half-lives = 10 min × (1 half-life/2 min) = 5 half-lives

For each half-life, you divide the total amount of the isotope by 2.

Amount remaining = original amount × 1/2^(number of half-lives)

Amount remaining = 33.4 g x $\frac{1}{2} ^ 5$ = 33.4 g × $\frac{1}{32}$ = 1.04 g

After 10 min, 1.04 g of barium-122 will remain.