The half-life period of a radioactive substance is 8 years. After 16 years, the mass of the substance will reduce from starting 16.0 g to

Options

A. 8.0 g
B. 6.0 g
C. 4.0 g
D. 2.0 g

Explanation

To solve the problem, we need to determine the remaining mass of a radioactive substance after a certain period, given its half-life. Here’s how to approach the problem step-by-step:

### Step-by-Step Solution:

1. **Identify the Half-Life**: The half-life of the radioactive substance is given as 8 years.

2. **Determine the Total Time Passed**: We need to find out how much time has passed, which is given as 16 years.

3. **Calculate the Number of Half-Lives**:
- Since the half-life is 8 years, we can calculate the number of half-lives that have passed in 16 years:
\[ \text{Number of half-lives} = \frac{\text{Total time}}{\text{Half-life}} = \frac{16 \text{ years}}{8 \text{ years}} = 2 \]

4. **Calculate the Remaining Mass**:
- The initial mass of the substance is 16.0 g. After each half-life, the mass is halved:
- After the first half-life (8 years):
\[ \text{Remaining mass} = \frac{16.0 \text{ g}}{2} = 8.0 \text{ g} \]
- After the second half-life (another 8 years):
\[ \text{Remaining mass} = \frac{8.0 \text{ g}}{2} = 4.0 \text{ g} \]

5. **Final Result**: After 16 years, the mass of the substance will reduce from 16.0 g to 4.0 g.

### Conclusion:
The mass of the radioactive substance after 16 years will be **4.0 g**.

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