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).
How many grams of cobalt-60 will remain after three half-lives? Answer: A Explanation: Cobalt-60 will have 0.125 grams remaining after three half-lives, which is closest to 1.25 grams (choice C).