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The half-life of a radioactive isotope is the time it takes for a quantity of the isotope to be reduced to half its initial mass. Starting with 175 grams of a radioactive isotope, how much will be left after 4 half-lives?

Question

The half-life of a radioactive isotope is the time it takes for a quantity of the isotope to be reduced to half its initial mass. Starting with 175 grams of a radioactive isotope, how much will be left after 4 half-lives?

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Solution

To determine how much of the radioactive isotope will be left after 4 half-lives, we can follow these steps:

  1. Identify the initial mass: The initial mass of the radioactive isotope is 175 grams.

  2. Understand the concept of half-life: After each half-life, the remaining quantity of the isotope is reduced to half of its previous amount.

  3. Calculate the remaining mass after each half-life:

    • After the 1st half-life: Remaining mass=1752=87.5 grams \text{Remaining mass} = \frac{175}{2} = 87.5 \text{ grams}
    • After the 2nd half-life: Remaining mass=87.52=43.75 grams \text{Remaining mass} = \frac{87.5}{2} = 43.75 \text{ grams}
    • After the 3rd half-life: Remaining mass=43.752=21.875 grams \text{Remaining mass} = \frac{43.75}{2} = 21.875 \text{ grams}
    • After the 4th half-life: Remaining mass=21.8752=10.9375 grams \text{Remaining mass} = \frac{21.875}{2} = 10.9375 \text{ grams}
  4. Conclusion: After 4 half-lives, the remaining mass of the radioactive isotope will be 10.9375 grams.

This problem has been solved

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