Gold (Au) has a synthetic isotope that is relatively unstable. After 25.5 minutes, a 128-gram sample has decayed to 2 g. What is the half-life of this isotope? O 1.5 minutes O 2.25 minutes O 8.5 minutes O 4.25 minutes

Algebra & Trigonometry with Analytic Geometry
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Chapter5: Inverse, Exponential, And Logarithmic Functions
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**Understanding Half-Life Calculation using Synthetic Isotopes**

Gold (Au) has a synthetic isotope that is relatively unstable. After 25.5 minutes, a 128-gram sample has decayed to 2 grams.

**Question:** What is the half-life of this isotope?

**Multiple Choice Options:**
- 1.5 minutes
- 2.25 minutes
- 8.5 minutes
- 4.25 minutes

**Explanation:**

To solve for the half-life of an isotope, we use the concept of exponential decay. The half-life is the time it takes for a substance to reduce to half its initial amount. For this isotope, we need to determine the number of half-lives it has undergone to decay from 128 grams to 2 grams in 25.5 minutes.

1. Start with the initial mass of the isotope: 128 grams.
2. After one half-life, the mass would be: \( \frac{128}{2} = 64 \) grams.
3. Continuing this process, we get:
   - Second half-life: \( \frac{64}{2} = 32 \) grams
   - Third half-life: \( \frac{32}{2} = 16 \) grams
   - Fourth half-life: \( \frac{16}{2} = 8 \) grams
   - Fifth half-life: \( \frac{8}{2} = 4 \) grams
   - Sixth half-life: \( \frac{4}{2} = 2 \) grams

Since it took 25.5 minutes to decay through 6 half-lives, we divide the total time by the number of half-lives to find the duration of one half-life:
\[ \text{Half-life} = \frac{25.5 \text{ minutes}}{6} = 4.25 \text{ minutes} \]

Thus, based on the calculation, the half-life of this synthetic isotope is 4.25 minutes. The correct answer is the last option:

- 4.25 minutes
Transcribed Image Text:**Understanding Half-Life Calculation using Synthetic Isotopes** Gold (Au) has a synthetic isotope that is relatively unstable. After 25.5 minutes, a 128-gram sample has decayed to 2 grams. **Question:** What is the half-life of this isotope? **Multiple Choice Options:** - 1.5 minutes - 2.25 minutes - 8.5 minutes - 4.25 minutes **Explanation:** To solve for the half-life of an isotope, we use the concept of exponential decay. The half-life is the time it takes for a substance to reduce to half its initial amount. For this isotope, we need to determine the number of half-lives it has undergone to decay from 128 grams to 2 grams in 25.5 minutes. 1. Start with the initial mass of the isotope: 128 grams. 2. After one half-life, the mass would be: \( \frac{128}{2} = 64 \) grams. 3. Continuing this process, we get: - Second half-life: \( \frac{64}{2} = 32 \) grams - Third half-life: \( \frac{32}{2} = 16 \) grams - Fourth half-life: \( \frac{16}{2} = 8 \) grams - Fifth half-life: \( \frac{8}{2} = 4 \) grams - Sixth half-life: \( \frac{4}{2} = 2 \) grams Since it took 25.5 minutes to decay through 6 half-lives, we divide the total time by the number of half-lives to find the duration of one half-life: \[ \text{Half-life} = \frac{25.5 \text{ minutes}}{6} = 4.25 \text{ minutes} \] Thus, based on the calculation, the half-life of this synthetic isotope is 4.25 minutes. The correct answer is the last option: - 4.25 minutes
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