Question

iodin is 80% ^127 I, 17% ^126 I, and 3% ^128 I. calculate the average atomic mass of iodine.

Answer 1

To calculate the average atomic mass of iodine, we can use the formula:

\[
\text{Average Atomic Mass} = \sum (\text{fraction} \times \text{isotope mass})
\]

where the fractions are the decimal representations of the percentages of each isotope.

Let's break it down for each isotope:

1. **Isotope \(^{127}\text{I}\)**:
- Percentage: 80%
- Fraction: \(0.80\)
- Atomic mass: \(127 \, \text{amu}\)
- Contribution: \(0.80 \times 127 = 101.6 \, \text{amu}\)

2. **Isotope \(^{126}\text{I}\)**:
- Percentage: 17%
- Fraction: \(0.17\)
- Atomic mass: \(126 \, \text{amu}\)
- Contribution: \(0.17 \times 126 = 21.42 \, \text{amu}\)

3. **Isotope \(^{128}\text{I}\)**:
- Percentage: 3%
- Fraction: \(0.03\)
- Atomic mass: \(128 \, \text{amu}\)
- Contribution: \(0.03 \times 128 = 3.84 \, \text{amu}\)

Now, we can add together all of the contributions:

\[
\text{Average Atomic Mass} = 101.6 + 21.42 + 3.84 = 126.86 \, \text{amu}
\]

Thus, the average atomic mass of iodine is approximately \( \mathbf{126.86} \, \text{amu} \).