Iron-55 has a half-life of 3 years. How much of a 40 gram sample will remain after 12 years? A. 0 grams B. 4 grams C. 2.5 grams D. 20 grams

Explanation:

We are asked to find how much of a 40 gram sample remains after 12 years.

Iron-55 has a half-life of 3 years. Therefore, after 12 years, 4 half-lives have been completed.

Every time a half-life is completed, half of the sample's mass decays. Remember we start with a 40 gram sample.

There is also a formula that can be used to solve this problem.

Where A₀ is the initial amount, t is the time, and hl is the half-life.

We know 40 grams is the inital amount, 12 years is the time, and 3 years is the halflife.

After 12 years, 2.5 grams of Iron-55 will remain.

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explanation: