5. If 800-ug of arsenic-76 are present in an artifact, how much arsenic-76 will be present after 132.5 hours? [SHOW WORK] The half-life of arsenic-76 is 26.5 hours.

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**Question:**

If 800 micrograms (ug) of arsenic-76 are present in an artifact, how much arsenic-76 will be present after 132.5 hours? The half-life of arsenic-76 is 26.5 hours. \[SHOW WORK\]

**Explanation:**

To answer this question, we'll use the concept of radioactive decay and half-life. The half-life is the time required for half of the radioactive substance to decay.

Here are the steps to solve the problem:

1. **Determine the number of half-lives:**
   
   The number of half-lives (\(n\)) that have passed can be calculated using the formula:

   \[
   n = \frac{\text{total time}}{\text{half-life}}
   \]

   Given:
   - Total time (\(t\)) = 132.5 hours
   - Half-life (\(t_{1/2}\)) = 26.5 hours

   \[
   n = \frac{132.5}{26.5} \approx 5
   \]

2. **Calculate the remaining amount of arsenic-76:**

   After each half-life, the amount of radioactive substance decreases by half. So, the remaining amount can be calculated using the formula:

   \[
   \text{Remaining amount} = \text{initial amount} \times \left( \frac{1}{2} \right)^n
   \]

   Given:
   - Initial amount = 800 micrograms
   - Number of half-lives (\(n\)) = 5

   \[
   \text{Remaining amount} = 800 \times \left( \frac{1}{2} \right)^5
   \]

   \[
   \text{Remaining amount} = 800 \times \frac{1}{32} = 25 \text{ micrograms}
   \]

Therefore, 25 micrograms of arsenic-76 will be present after 132.5 hours.
Transcribed Image Text:**Question:** If 800 micrograms (ug) of arsenic-76 are present in an artifact, how much arsenic-76 will be present after 132.5 hours? The half-life of arsenic-76 is 26.5 hours. \[SHOW WORK\] **Explanation:** To answer this question, we'll use the concept of radioactive decay and half-life. The half-life is the time required for half of the radioactive substance to decay. Here are the steps to solve the problem: 1. **Determine the number of half-lives:** The number of half-lives (\(n\)) that have passed can be calculated using the formula: \[ n = \frac{\text{total time}}{\text{half-life}} \] Given: - Total time (\(t\)) = 132.5 hours - Half-life (\(t_{1/2}\)) = 26.5 hours \[ n = \frac{132.5}{26.5} \approx 5 \] 2. **Calculate the remaining amount of arsenic-76:** After each half-life, the amount of radioactive substance decreases by half. So, the remaining amount can be calculated using the formula: \[ \text{Remaining amount} = \text{initial amount} \times \left( \frac{1}{2} \right)^n \] Given: - Initial amount = 800 micrograms - Number of half-lives (\(n\)) = 5 \[ \text{Remaining amount} = 800 \times \left( \frac{1}{2} \right)^5 \] \[ \text{Remaining amount} = 800 \times \frac{1}{32} = 25 \text{ micrograms} \] Therefore, 25 micrograms of arsenic-76 will be present after 132.5 hours.
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