How many grams of cobalt-60 will remain after three half-lives?

Cobalt-60 Decay Calculation

Cobalt-60 is a radioactive isotope that undergoes radioactive decay. The half-life of cobalt-60 is 5.27 years. This means that after 5.27 years, half of the original cobalt-60 sample will have decayed.

To calculate how many grams of cobalt-60 will remain after three half-lives, we can use the formula:

Amount remaining = Initial amount x (1/2)^(number of half-lives)

Let's denote the initial amount of cobalt-60 as 1 gram. After three half-lives, the number of years that have passed is 3 x 5.27 = 15.81 years.

Plugging in the values into the formula:

Amount remaining = 1 gram x (1/2)^(3) = 1 gram x (1/8) = 0.125 grams

Therefore, 0.125 grams of cobalt-60 will remain after three half-lives. The closest answer choice to this calculation is 1.25 g (C).